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As in our previous video we started building some amount of intelligence store windows form.

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We added a click event such that when we fill out the information and select the type of car click submit.

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Then we get a message box displaying the data that was entered.

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Now in this video what we want to do is add some more functionality or some more intelligence to the

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submission.

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We want to add some validation things that maybe the customer name and so we want to make sure that

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when the person clicks submit the customer name and the car type we need to make sure that values have

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been entered focus of my name and selected for the car type.

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We also want to make sure that the dates are at least maybe the date return should not be in the POS

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or further into POS than be rented.

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You know things that that so dates oriented kinds of a future date when compared to date returns so

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we're going to add some intelligence for that and we'll also look at potential exceptions that could

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occur while we are doing our operation.

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So to start this off I'm one to modify my form a bit and what I'm want to do is add a new field and

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I'm going to call this field cost someone to go to my tool box.

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I'm going to started the display so for some reason to need my tools so I know it's displaying many

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more than I need but ultimately directly technically.

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So all.

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And then it brought all of them.

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So if you if you're a tool box or to the selections instead of your tool box disappear begin to right

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click in the pin and click show all or go to choose items and so that the ones you want.

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Right now I'm interested in common controls because I'm about to bring over a new text box.

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Drag it over and get my arrow.

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That's fine and I'm going to use this text box to allow the user to enter the costs on the stake in

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text box.

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I'm copying an existing label so I don't have to do cooking on the rework.

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Changing the property changing the text from customer name to cost.

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All right so if the expectation is that when the person is entering this record they enter the customer

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name the cost the beer into the returned and the type of car.

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No I'm going to rename the text box as we know we have developed the discipline to do because I don't

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want to have to know if it's six bucks one hour or not so using my naming convention which is to put

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the prefix TB so I'm going to see TB cost.

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All right so I know I have a cost textbooks are textbooks named costs are for the cost.

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So no I'm just going to modify my code and to get the cost I'm storing my cost as a double.

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All right.

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So I say double cost is equal to and then it would be so easy to just say TB cost not text right.

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Because that's all we know we get the text from the textbooks.

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But here's our problem.

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We're seeing that we have a red line and it C cannot implicitly convert type string to double.

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That's because text is a string and I'm trying to store the cost inside of a numeric data type which

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we know is illegal because C sharp is so strongly typed so I need to do a conversion.

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So I want to say convert dots to double and then I'm passing in the values that is in the text box.

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So what this does is it gets the takes from the text box then it converted to a double and then we store

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it inside of our variable double cost.

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Now remember that we could actually just call these variables var if we wanted to.

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So if you want to change them all that's fine I won't do it but at least we know the options that we

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have.

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After adding the cost what I'm want to do is add that data to the message box that's being printed so

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I'm just going to duplicate one of the lines and change the text accordingly cost.

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So I control D on this line we'll duplicate the line and all I'm doing is changing out the data so no

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cost is printed in my message box.

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Now before I get to the message box though I want to make sure that all the the data is available or

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is provided before it gets to it.

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So this should only get printed when everything is in place everything is successfully entered into

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the form.

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So I need to check and make sure that the customer name is available and that the type of car at the

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very least those tools should have been selected so the tool I can use for this is a simple statement

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I can simply see if the string was provided or if the value was provided then or if it wasn't provided

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rather then there is an error.

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So what I can see and I love to check the negatives first in my code I can see if customer name right.

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And then if you have programming experience or from other languages then maybe other languages would

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allow you to see is equivalent to no.

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And that seems fine because what we're checking is to see if the customer and field which we stored

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in the customer name field which is stored in the variable customer name we're checking if the value

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is no.

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That seems fine but then if it is a blank string then it's technically not low.

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So that comparison would not yield the result that we really want.

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So C sharp actually uses some string manipulation tools so I can see I can call it the data type string

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and then I can see a dot and then I will see that I have two functions here I have one that says isn't

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a large empty indicates where whether the specified string is no are empty or is what null are whitespace

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which indicates if it is no empty or consists of only whitespace characters right.

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Somewhat to choose is null or whitespace so you can choose either but isn't the law why space seems

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a bit more comprehensive in terms of what we're checking some way to use isn't a large whitespace then

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pass in the string that I'm checking to see if this string is null or contains wide spaces are it's

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just empty whatever it is that is supposed to be to return true or false right.

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Someone to say if this obtains if this is true or if the car type also is no la empties I can see if

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either one of these is no longer whitespace.

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Using the lower whitespace so if either one of these is null or contains whitespace or is empty then

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I want to display a message box that says please provide missing data please enter missing data.

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All right.

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And then as again see I'm not you know based on the fact that I'm checking for both of them at the same

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time.

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I.

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It limits my ability to be specific.

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Right.

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So if I had and if statements are a condition for the customer name alone then I could specifically

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say you're missing the customer name.

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If I had one for the car type of loan that I could specifically say you're missing the car type.

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The downside over is that I don't want to show a message box for every single error that is there one

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message box that aligns all the arrows would be nice right.

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So right now I'm just saying one message box with a generic error message based on the.

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If either one of these conditions evaluates to true.

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All right.

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Another tip that I indicated I wanted to do was on the dates because I'm getting it in and I'm getting

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dates out or dates all 10 dates in art.

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So I want to make sure that the date out doesn't have a greater data value than date in because that

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wouldn't make sense it would make sense that I see the dates or instead is the 20th of February but

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the date returned was the 1st of February.

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That's not practical.

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Right.

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So that is illegal somewhat to add another statement and I'm going to say so.

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No I'm going to specifically check for this when I have a specific message box error for this and then

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later we're going to refer to the code and make it a bit easier to or a bit more efficient in displaying

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the error messages but for no let's just work on it the way you know.

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Case by case.

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So I'm going to see if then these two are data values so it's easy enough for you as a human to compare

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two dates is February 20 greater dates then February 1.

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And that would be true.

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February 20 is agreed to date and February 1.

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So if we wanted to do this comparison I could see if the date.

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Oh it is agreed to then the date in then we have an error right.

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So dates all being the dates rented should never be greater than the date in being the date returned.

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So I can see if debt owed is greater than date in and then we display a message box seeing illegal dates

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elections and I just copy and paste that one and change the text illegal date selection.

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All right but then you noticed that I have a red line in my line thirty four with this comparison.

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And that's because we're comparing two strings it seeing you cannot use the grid to then operator when

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comparing strings.

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So this greater than operator is usually used for numbers like if I wanted to give one number is greater

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than the other if one numeric variable is greater in value than the other.

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Then fine but then I kind of compare two strings which then tells me that the way I'm handling my data

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values is inhibiting my ability to properly manipulate these values someone to go back changed my code

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a bit.

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What I'm going to do is change these notes to date time.

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So the going back to our design our eight speaker control actually returns a date time value by default.

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Right.

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So I was the one trying to convert it to a string here.

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But the value itself if we hover over our value to see that it says the time and date time can also

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be compared.

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Can be compared.

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Just like all integers and doubles and other numeric values can be compared.

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So what I'm going to do is change my code a bit and I'm not going to convert it to a string since that

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I'm getting the value and then I'm getting it error because we're putting added time inside of a string

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so I need to change my data type so no I'm just going to shortcut it and use var.

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All right.

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So var is going to make my variable take on the identity of the value of being assigned to it.

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So I'm assigning idea times I hover over the variable and all of a sudden it is at the time.

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All right.

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I noticed that my error.

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It went right away.

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So I'm checking if this daytime value is greater than this daytime value.

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So it's oats should not be greater than dates in and if it is then I'm going to display the illegal

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message.

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All right.

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The next thing that's I'm want to do in terms of the logical flaw is try and put something in place

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that it won't display this success message.

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If these conditions are true.

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All right.

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You know instinctively you're probably going to say oh but we could have said if then else if and then

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else.

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And you wouldn't be wrong.

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But then I wouldn't write it that way and I'm not one to write it that way because when we have an if

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then else if then else only one blog can evaluate the truth so that means if we say if then as if then

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else then we would only get to see one error message that is wrong with the form.

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So it's philosophical right.

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I mean there's no one way to do this because you could do it that way and you could say if this is true

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then nothing else executes if this is false.

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Else if this is true then nothing else executes.

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And then if neither one of these evaluates to true then that as would trigger and then this would be

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true and this would be displayed.

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However I want to make it that I want to show the user everything that is wrong with the farm when something

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is wrong with the farm.

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So that's why I made this statement.

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And in this Mrs. Boxer the show and this is statements this one will show also if both of these are

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wrong but then I don't want this to show at all.

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So I'm just going to put in a new variable and I'm going to call it var is valid and I'm going to set

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this to true.

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All right.

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So I'm declaring a boolean called is valid right.

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I'm calling it is valid there's no particular reason for me naming it that way.

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It's just indicative of the fact that it is tracking if the farm is in a valid states are not right.

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So VAR is valid and because I signed a valid true it is a boolean no if this condition is true and we're

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not we're going to discipline error then we know that the farm is not valid.

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All right.

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So I'm going to change the value of is valid if this statement is true then is valid is no longer true.

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All right.

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So is valid is no equal to False so once again we start off by setting it as true we want it to be true

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we hope that this form is valid but then we are going to check no for the invalid Parramatta's and the

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first of which is if the customer name or the car type was not provided then we're going to say well

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it is not valid.

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If this was not met then is valid is still true because then if this condition wasn't met then it didn't

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go in and she is a valid state or value.

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But then if the death toll is greater than the date in then the form is not valid.

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So is valid is false here.

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All right.

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So both of these will check and see that there is valid state is false.

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And then what I'm going to do in this last night is see if it is valid is equivalent to true then we

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want to proceed all right.

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So then if if is valid is true then we print our success message so it does put the success message

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instead of block knowing C sharp you can actually write this as if is valid.

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So you have two ways to write that you can see.

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Let me just read a comment.

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You can say if is valid is equivalent to truth they can write so the entire statement if it is true

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but then when you're dealing with a boolean you're really seeing if this is true.

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And then if you wanted to give it as far as against it if it is not true by just putting the exclamation

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sign instead of seeing if is valid it is equivalent to false.

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All right.

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So you can write it that Chakotay way.

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That's a nice school way to write it most programming languages elevator at it this way.

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And I'm just leaving this comment there so you can see exactly the alternatives you have.

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So if you feel more comfortable writing this way that's entirely fine.

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So let's go through this one more time.

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So we set a flag to check the validity of our forum.

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I'm just saying is valid is true.

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So when we collect all the information from the farm whereas assuming that everything is intact and

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the validity is true then we start seeing if the customer name is not provided or the car type is not

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provided then the is valid is null falls and we display the error message.

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We also check if the debt owed is greater than the date in if that holds true then it is invalid.

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And so we change a flag and display an error message.

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Now at the end of all of that we're checking to see if there is valid value is still true because if

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neither of these conditions was met then is valid is still true and if it is valid is still true then

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we display our success as long as is valid as value didn't change from true until we got here then it

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is success.

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All right so let's distort our new logic so we just click start and then I'm going to fill out the form

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for someone to keep it you know based on what we know so put in the custom of putting the cost puts

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in the type of car click submit and then it's good to say that illegal data selection.

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That's because I'm checking that the dates are printed should be greater than the date return right

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here.

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I didn't change the values on there both defaulting to the same day.

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So if I mean that's adjustment so you see that one of our validations is working I click submit and

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then we see that everything is okay.

221
00:17:34,490 --> 00:17:34,890
All right.

222
00:17:35,270 --> 00:17:36,530
No let's start breaking it.

223
00:17:36,530 --> 00:17:42,560
If I change the date rented to the fifth and the day returned is the third or the date.

224
00:17:42,580 --> 00:17:49,330
Oh it is no greater than the date in then when I click Submit illegal dates selection.

225
00:17:49,370 --> 00:17:49,860
All right.

226
00:17:50,090 --> 00:17:57,650
So we're seeing that it is hitting this if statement if we want to be more more strategic in seeing

227
00:17:57,650 --> 00:18:01,560
exactly what the court is doing we can add break points that we're already in debug mode.

228
00:18:01,610 --> 00:18:06,880
We can go back to visual studio and a breakpoint somewhere to add this breakpoint to the fore.

229
00:18:06,960 --> 00:18:09,900
Let's put it to the last variable declaration.

230
00:18:10,010 --> 00:18:10,790
All right.

231
00:18:10,790 --> 00:18:12,200
And then let's try this again.

232
00:18:12,200 --> 00:18:18,990
So I want to take all customer any in this time and then I'm going to click submit.

233
00:18:19,010 --> 00:18:24,500
And then what happens is that it hits that and then using if you live you can go line by line.

234
00:18:24,500 --> 00:18:29,990
So when you see that line highlighted in yellow it means that your breakpoint or your code execution

235
00:18:29,990 --> 00:18:31,490
is not that line.

236
00:18:31,490 --> 00:18:35,840
If you hit F 11:00 it will go to the next line and then line by line.

237
00:18:35,840 --> 00:18:37,100
You can track what's happening.

238
00:18:37,130 --> 00:18:44,410
So if I look in this variable I see that it has no data or its customer name blank string.

239
00:18:44,450 --> 00:18:47,740
If I looking car type I see that Honda is provided.

240
00:18:47,750 --> 00:18:54,560
However when I step through and I go to if you live in again it no goes into this statement because

241
00:18:54,560 --> 00:18:58,460
then this condition was just evaluated to be true.

242
00:18:58,460 --> 00:19:05,090
And so where it's seeing that the farm is not valid and then if 11 and then it goes to the message box

243
00:19:05,090 --> 00:19:12,590
and we see a message box enter missing data we click all key but then the execution is done and it continues

244
00:19:12,590 --> 00:19:18,950
and we say if you live in and then we see that the date out which is the 5th of February is greater

245
00:19:18,950 --> 00:19:22,170
than the date in which is a third of February.

246
00:19:22,250 --> 00:19:29,510
And if we if 11 it goes in again I need to make sure that it knows that the date the validity is false

247
00:19:30,440 --> 00:19:32,930
and then it displays that message box again.

248
00:19:32,930 --> 00:19:36,770
So we have two message boxes being displayed and then it continues.

249
00:19:36,770 --> 00:19:43,010
So if you live in and then we'll go to is valid no if is valid is checking if it's valid is true.

250
00:19:43,040 --> 00:19:44,860
Right right.

251
00:19:44,860 --> 00:19:50,640
No it is falls because if it wasn't said the first time it was definitely set the second time.

252
00:19:50,860 --> 00:19:56,440
And so because it's false it's actually skips over that statement and then continues.

253
00:19:56,440 --> 00:20:04,690
No at this stage we can just hit F5 for it to continue to execution or we can just click continue.

254
00:20:04,690 --> 00:20:09,250
And so we would have gotten the two message boxes because we had two arrows prisons.

255
00:20:09,250 --> 00:20:10,000
All right.

256
00:20:10,120 --> 00:20:14,980
So we see that's our validation code is work and doesn't seem we if I didn't provide a value for type

257
00:20:14,980 --> 00:20:19,420
of car we would have gotten that error message both entering missing data.

258
00:20:19,420 --> 00:20:27,850
No I'm going to run one more experiment and then show you another way that we need to code for validation.

259
00:20:27,850 --> 00:20:30,040
So I'm not willing to provide up cost.

260
00:20:30,040 --> 00:20:30,360
All right.

261
00:20:30,390 --> 00:20:32,950
So no cost will be provided.

262
00:20:32,950 --> 00:20:39,830
And then I'm going to hit submit and then you're going to see my code break right before your eyes.

263
00:20:39,830 --> 00:20:45,970
So we're getting some form of exception where see in the input string was not in a card format.

264
00:20:45,980 --> 00:20:46,270
All right.

265
00:20:46,280 --> 00:20:53,150
So what is happening here is that we did not provide a string for the cost and then it is trying to

266
00:20:53,150 --> 00:20:54,290
convert it to double.

267
00:20:54,290 --> 00:20:59,300
So essentially this is saying that I cannot convert nothing to a number.

268
00:20:59,300 --> 00:20:59,760
Yes.

269
00:20:59,780 --> 00:21:02,820
As a human you probably seeing but nothing as a number is zero.

270
00:21:02,840 --> 00:21:08,120
But a computer is seeing zero as something and nothing as literally nothing.

271
00:21:08,130 --> 00:21:08,780
Right.

272
00:21:08,810 --> 00:21:13,070
So it is seeing here that I cannot do this conversion.

273
00:21:13,070 --> 00:21:14,900
I don't know what to do here.

274
00:21:14,990 --> 00:21:17,660
And then these are what we call exceptions.

275
00:21:17,690 --> 00:21:22,970
So when we have an exception it can break our program and if I could continue to see that it exits the

276
00:21:22,970 --> 00:21:24,460
program automatically.

277
00:21:24,470 --> 00:21:24,800
Right.

278
00:21:25,220 --> 00:21:30,830
So when you're using your applications and you get those feet to Arizona equal again then the entire

279
00:21:30,830 --> 00:21:32,280
program closes.

280
00:21:32,300 --> 00:21:33,750
Those are exceptions.

281
00:21:33,860 --> 00:21:40,370
We want to reduce the number of exceptions or the likelihood that exceptions will occur and end the

282
00:21:40,420 --> 00:21:43,070
runtime or the running of our program.

283
00:21:43,070 --> 00:21:50,690
So we use exception handling because we can code defensively to some extent and we might not be able

284
00:21:50,690 --> 00:21:54,470
to code defensively to much further extent.

285
00:21:54,500 --> 00:22:02,240
So the try catch is literally the catch all that helps us to navigate around those occurrences.

286
00:22:02,240 --> 00:22:07,510
So what I'm going to introduce to this button click event is tracking.

287
00:22:07,540 --> 00:22:11,320
So going back to my first line I'm going to say try.

288
00:22:11,330 --> 00:22:16,970
So I just write Trey and then I'm going to press stop twice and it generates the entire block for me.

289
00:22:17,000 --> 00:22:22,170
So I'm trying an operation and then I'm catching an exception.

290
00:22:22,230 --> 00:22:22,900
Right.

291
00:22:22,970 --> 00:22:31,340
So let me just start by taking everything that we were doing inside of this application instead of this

292
00:22:31,340 --> 00:22:34,760
click event so adjust the code that we wrote.

293
00:22:34,760 --> 00:22:39,770
So be careful with the braces that spoke to this last brace off this statement.

294
00:22:39,770 --> 00:22:40,730
You cut that.

295
00:22:40,910 --> 00:22:47,900
And then you put it inside of the tray all right so we're trying all of these operations and not it.

296
00:22:47,910 --> 00:22:54,320
It stopped executing on the twenty seventh line or on the line where we're converting the double that

297
00:22:54,330 --> 00:22:55,550
takes to double.

298
00:22:55,590 --> 00:22:57,830
So that is the problem line.

299
00:22:57,870 --> 00:23:01,740
It doesn't have to be a problem but that's the one we've detected so far.

300
00:23:01,740 --> 00:23:08,270
The point is that I'm trying all of this wherever it feels in attempting any of this code.

301
00:23:08,280 --> 00:23:10,340
Then we go over to the catch.

302
00:23:10,380 --> 00:23:16,950
So when one of those arrows like we just saw with the conversion when that kind of error occurs then

303
00:23:16,950 --> 00:23:19,770
we catch it we catch that error.

304
00:23:19,770 --> 00:23:27,150
No I'm going to extend this catch and I'm going to put the exception into an object called E X which

305
00:23:27,180 --> 00:23:31,320
allows me to get the details of the exception being thrown.

306
00:23:31,320 --> 00:23:34,890
So that error message is a visual studio showed up both invalid.

307
00:23:34,890 --> 00:23:42,070
System Error and this and that on that I can actually get that wording from this object that I'm attaching

308
00:23:42,080 --> 00:23:43,040
to the exception.

309
00:23:43,060 --> 00:23:43,350
Right.

310
00:23:43,890 --> 00:23:55,380
So then I can display a message box specifically inside of the exception and then I can see that the

311
00:23:55,380 --> 00:23:59,610
exception or the message that I want to show is e x.

312
00:23:59,640 --> 00:24:02,850
So that's the object for the exception dot.

313
00:24:02,850 --> 00:24:05,400
And then it has message.

314
00:24:05,400 --> 00:24:06,330
All right.

315
00:24:06,330 --> 00:24:12,150
So then I can display the message saying that you know this is the problem that you're encountering

316
00:24:13,080 --> 00:24:16,380
the throttle would actually end the program.

317
00:24:16,380 --> 00:24:20,670
No you can make a decision do you want to end the program when there's an exception or do you want to

318
00:24:20,670 --> 00:24:26,440
continue with the program even though there's an exception so I can just remove the through our comments

319
00:24:26,450 --> 00:24:27,310
into told for no.

320
00:24:27,320 --> 00:24:32,880
But you can delete it if you want but the throw once again will end the program if you don't have the

321
00:24:32,880 --> 00:24:35,960
throw it will display the message box you click Okay.

322
00:24:36,180 --> 00:24:38,190
But then you still have your program running.

323
00:24:38,190 --> 00:24:39,570
So let's see how that works.

324
00:24:40,080 --> 00:24:41,790
So I go back to start.

325
00:24:41,970 --> 00:24:46,860
And then this time I want to test and make sure that my exception handling works someone to provide

326
00:24:46,860 --> 00:24:50,020
the data that I know needs to be provided.

327
00:24:50,100 --> 00:24:57,270
Change the date and then click submit and then you see input stream was not in a car for months.

328
00:24:57,270 --> 00:25:03,240
So what happened was it tried the operation it got up to the part where it tried the conversion and

329
00:25:03,240 --> 00:25:06,680
then it realized that OK I can't do this.

330
00:25:06,690 --> 00:25:08,680
It went down to catch the exception.

331
00:25:08,790 --> 00:25:15,060
And then that is the message inside of the exception because we didn't type anything in a message box

332
00:25:15,060 --> 00:25:15,750
to see this.

333
00:25:15,750 --> 00:25:16,290
Right.

334
00:25:16,290 --> 00:25:21,600
So this message box is displaying the message for that particular exception.

335
00:25:22,260 --> 00:25:28,160
So you see even though we can code defensively against fees that we're expecting or conditions that

336
00:25:28,170 --> 00:25:31,040
we're expecting business rules that we're enforcing.

337
00:25:31,110 --> 00:25:36,450
Sometimes the system itself may have an error that you could not have accounted for.

338
00:25:36,480 --> 00:25:39,880
So that is the where the try catch comes in handy.

339
00:25:39,930 --> 00:25:46,190
We can get certain exceptions and not let them in the program you know completely.

340
00:25:46,300 --> 00:25:51,540
Now as a final act I'm just going to modify the way we're displaying the message boxes.

341
00:25:51,540 --> 00:25:52,210
All right.

342
00:25:52,230 --> 00:26:00,000
So instead of this being a message box per error what's I'm going to do is have a string where I'm going

343
00:26:00,000 --> 00:26:07,140
to compile the errors and then if is valid these forms then we display that message box with all the

344
00:26:07,140 --> 00:26:09,290
compiled sentences of errors.

345
00:26:09,300 --> 00:26:12,240
So right now we have two error situations.

346
00:26:12,240 --> 00:26:14,370
We have this one and we have this one.

347
00:26:14,370 --> 00:26:15,940
We have two message boxes.

348
00:26:15,990 --> 00:26:24,270
What I'm going to do is this clear a new variable var error message but I'm making this one equal to

349
00:26:24,270 --> 00:26:25,110
an empty string.

350
00:26:25,140 --> 00:26:31,470
So I'm starting off with an empty error message because up until this point we're assuming that the

351
00:26:32,040 --> 00:26:33,820
form is valid.

352
00:26:33,820 --> 00:26:34,590
Right.

353
00:26:34,620 --> 00:26:37,130
And then the error message would be empty.

354
00:26:37,140 --> 00:26:46,470
So instead I'll see error message box that show I'm going to see instead error message.

355
00:26:46,470 --> 00:26:51,380
And then we can do a little operation here which is a plus equals.

356
00:26:51,770 --> 00:26:52,110
All right.

357
00:26:52,110 --> 00:26:55,620
So we're just saying we're compiling this string.

358
00:26:55,620 --> 00:26:56,010
All right.

359
00:26:56,190 --> 00:27:01,640
So we're seeing error message plus equals please enter missing data.

360
00:27:01,670 --> 00:27:06,230
And then I'm just going to add the new line operator right there right.

361
00:27:06,240 --> 00:27:10,170
So in case there are multiple lines that will be there at all on all the lines.

362
00:27:10,170 --> 00:27:16,500
So I can refine this a bit so I can see error please enter missing data.

363
00:27:16,530 --> 00:27:25,320
So if the customer name on the card type are not provided then I see the validity of the form is on

364
00:27:25,320 --> 00:27:32,640
all fours and then I'm adding an error message to the variable that I already created.

365
00:27:32,640 --> 00:27:32,910
Right.

366
00:27:32,910 --> 00:27:37,110
So it starts off blank and then if this is true then no it has some content.

367
00:27:37,140 --> 00:27:44,240
So I'm seeing whatever was there before I that this or this string whatever was there before.

368
00:27:44,240 --> 00:27:45,250
That's what the Plus equal.

369
00:27:45,260 --> 00:27:47,170
It's an accumulation right.

370
00:27:47,180 --> 00:27:50,020
So we would probably be used to this with math.

371
00:27:50,090 --> 00:27:53,320
Well in C sharp you can use it again strings also.

372
00:27:53,350 --> 00:27:58,880
So I'm someone to do the same thing though below I'm going to see if the date out is greater than the

373
00:27:58,880 --> 00:28:04,370
dates in then I also want to accumulate this error message onto this string.

374
00:28:04,370 --> 00:28:07,790
So I'm just going to say this new line character puts it into the string.

375
00:28:07,790 --> 00:28:14,600
Take all this extra brace and so if either one of these are if both of them are successful then we're

376
00:28:14,600 --> 00:28:19,640
just compiling the error message and that is valid would have changed anyway.

377
00:28:19,730 --> 00:28:27,410
No I can put in that if as though in here to say if is valid then display a message box with the success

378
00:28:27,760 --> 00:28:37,210
and then I'm going to see who else I want a message box so a message box that show and then I am one

379
00:28:37,210 --> 00:28:44,410
to display the arrow message whatever the contents of our message are open to this point I want to print

380
00:28:44,410 --> 00:28:46,690
them out instead of the message box.

381
00:28:46,720 --> 00:28:51,790
So that means if you add another scenario tomorrow where you have another statement for the validity

382
00:28:52,090 --> 00:28:55,990
then I can just add the error message and see what is wrong.

383
00:28:55,990 --> 00:28:59,390
So just for to put in the word there.

384
00:28:59,410 --> 00:29:00,160
All right.

385
00:29:00,160 --> 00:29:03,160
So I'm just showing you that there are so many ways you can do this.

386
00:29:03,180 --> 00:29:05,500
I'm not saying this is the way to do it.

387
00:29:05,500 --> 00:29:07,090
I'm not saying this is a standard.

388
00:29:07,090 --> 00:29:10,150
I'm not saying that this is you know there is no other way.

389
00:29:10,300 --> 00:29:12,410
I want you to have your individuality.

390
00:29:12,430 --> 00:29:12,930
Sure.

391
00:29:12,940 --> 00:29:17,890
I'm just showing you that there are so many ways to do this once you accomplish what you need to do

392
00:29:18,220 --> 00:29:24,250
and with maybe fewer lines of code the jury results on with a few lines of code means more efficient

393
00:29:24,250 --> 00:29:24,700
or not.

394
00:29:24,950 --> 00:29:27,940
But the fact is if you can accomplish it then that's good.

395
00:29:27,940 --> 00:29:30,880
So it lets us test and see what this would look like.

396
00:29:30,880 --> 00:29:38,350
So if I start the application all right and then I submits always happen when I submit is that it's

397
00:29:38,350 --> 00:29:40,000
going to bomblets on this line.

398
00:29:40,000 --> 00:29:45,550
So if I submits with everything blank it tries to convert the empty string to cost and it's just going

399
00:29:45,550 --> 00:29:46,360
to catch the error.

400
00:29:46,390 --> 00:29:48,550
So if I click submit you see them straight.

401
00:29:48,550 --> 00:29:51,220
So they catch and is displaying that error.

402
00:29:51,250 --> 00:29:52,650
So that's fine.

403
00:29:52,660 --> 00:30:00,130
Well let's provide up costs and then let's try again if I click submit no it's seeing object not set

404
00:30:00,130 --> 00:30:07,720
to instance of an object reference that's in an instance of an object which I can tell you we didn't

405
00:30:07,720 --> 00:30:09,940
write that error so that's another exception.

406
00:30:09,940 --> 00:30:15,010
So no we need to debug and see exactly what we're missing why we're getting that error.

407
00:30:15,010 --> 00:30:22,140
So if I put my breakpoint at the start of the line saw that it was minimized but my breakpoints and

408
00:30:22,140 --> 00:30:25,370
no I'm bringing back my window and I click submit.

409
00:30:25,450 --> 00:30:28,770
So I'm going to step through until I see where it jumps 0.

410
00:30:28,840 --> 00:30:35,110
So as far as you can see once it goes to the next line everything is key.

411
00:30:35,120 --> 00:30:35,510
Right.

412
00:30:35,920 --> 00:30:42,700
So it's go into the next line and then I think it's this line and seeing that the object's reference

413
00:30:42,730 --> 00:30:44,260
is not set to anything.

414
00:30:44,270 --> 00:30:48,650
So I'm here trying to convert nothing to string.

415
00:30:48,670 --> 00:30:49,040
Right.

416
00:30:49,060 --> 00:30:56,240
So the selected item is no I'm trying to convert nodes a string and then I am guaranteeing that when

417
00:30:56,240 --> 00:30:59,140
I Priscilla it's going to go straight into the catch.

418
00:30:59,140 --> 00:31:00,400
And there we go.

419
00:31:00,400 --> 00:31:02,060
All right.

420
00:31:02,200 --> 00:31:06,000
So then that's another thing that we didn't account for.

421
00:31:06,000 --> 00:31:06,310
All right.

422
00:31:06,310 --> 00:31:11,660
So that means we need to kind of change the way that we're getting the value from the combo box.

423
00:31:11,670 --> 00:31:16,710
So another way to get the value from the combo box could be the text.

424
00:31:16,720 --> 00:31:24,160
So I'll use the text so that text would get the value from the combo box and I made up code change while

425
00:31:24,160 --> 00:31:25,200
I'm in debug mode.

426
00:31:25,210 --> 00:31:28,440
So I actually have to restart the application.

427
00:31:28,440 --> 00:31:28,740
All right.

428
00:31:29,110 --> 00:31:34,690
So that text would give me the text that is being displayed in the combo box if there is no text being

429
00:31:34,690 --> 00:31:36,720
displayed then it's a blank string.

430
00:31:36,940 --> 00:31:44,050
That is C for as we're seeing if we tried the way that we had it before we're going to get an exception

431
00:31:44,410 --> 00:31:47,700
and we might not be able to properly tell the person.

432
00:31:47,710 --> 00:31:49,120
Sorry about that.

433
00:31:49,120 --> 00:31:52,240
Roman I'll be able to propagate it to the person what's wrong.

434
00:31:52,240 --> 00:31:55,820
So using the DOT text is probably easier.

435
00:31:55,840 --> 00:31:58,540
So let me just restart this application.

436
00:31:58,750 --> 00:32:04,240
Once again we restarted because if we make a code change while we're in debug mode it doesn't register

437
00:32:04,600 --> 00:32:11,030
and to restart all I did was click this our circular our B service stop button and pause buttons.

438
00:32:11,040 --> 00:32:11,280
Right.

439
00:32:11,740 --> 00:32:13,090
So let's try this again.

440
00:32:13,090 --> 00:32:17,680
So once a chance of costs when we saw the cost validation work.

441
00:32:17,700 --> 00:32:21,420
It jumped to the exception and then I'm going to click submit.

442
00:32:21,450 --> 00:32:25,130
But before I did let me take my break point because I don't want to break point.

443
00:32:25,150 --> 00:32:26,680
I don't have to step through.

444
00:32:26,710 --> 00:32:33,370
So taking all the break points I'm clicking submit and then we're seeing our message box with arrows.

445
00:32:33,370 --> 00:32:37,850
Error Please enter missing data error illegal data selection.

446
00:32:37,850 --> 00:32:38,410
All right.

447
00:32:38,470 --> 00:32:46,180
If I change one of them so put in the customer name and click submit then I'm only going to see oh well

448
00:32:46,180 --> 00:32:48,000
it's still seeing enter missing data.

449
00:32:48,000 --> 00:32:48,340
So.

450
00:32:48,640 --> 00:32:53,620
So that's another thing too because I'm checking for both customer name and type of guy in the same

451
00:32:53,740 --> 00:32:54,540
statement.

452
00:32:54,550 --> 00:32:58,250
It's hard to be individual All right.

453
00:32:58,270 --> 00:33:04,930
I mean I could probably miss it fill the toilet and say Please enter customer name and the type of car

454
00:33:05,230 --> 00:33:06,710
I could be explicit.

455
00:33:06,820 --> 00:33:10,090
So obviously 5 1 I'm not the other than the user could deduce.

456
00:33:10,090 --> 00:33:10,930
So that's fine.

457
00:33:10,930 --> 00:33:14,630
You could change a message or you could change the number of blocks.

458
00:33:14,680 --> 00:33:16,180
I won't prioritize that right.

459
00:33:16,180 --> 00:33:16,840
No.

460
00:33:16,840 --> 00:33:22,730
But let me just produce the type of car click submit and then we're seeing one error message noticing

461
00:33:22,760 --> 00:33:24,830
seeing illegal data selection.

462
00:33:24,850 --> 00:33:33,130
And then we changed that to three and then click submit and know we have a valid farm and valid data

463
00:33:33,160 --> 00:33:36,100
being inserted.

464
00:33:36,160 --> 00:33:36,530
All right.

465
00:33:36,560 --> 00:33:42,590
So that's pretty much it for building in some validations once again this is not an exact science.

466
00:33:42,590 --> 00:33:44,800
This is not an exact right.

467
00:33:44,840 --> 00:33:47,000
This is the way it has to be done.

468
00:33:47,000 --> 00:33:52,000
This is just a guide giving you some ideas as to how you could go both validating what you need to look

469
00:33:52,000 --> 00:33:58,570
out for how to properly handle when there are genuine errors that you have not accounted for without

470
00:33:58,670 --> 00:34:01,020
ending the runtime of your program.