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Hey guys welcome to another exciting video in our journey with a speed that MVC web development.

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Today we will be looking into adding validations to our farms.

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Now validations are very important because when we are accepting input from a user trying to storage

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in our database we want to ensure that whatever we're passing with the database meets certain rules

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at the very least a rule can be like you expect a text value for text field or the expected number value

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for a number of fields or your text value should be at a certain length.

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Those kinds of things those are validations that you want to ensure we do from the client side meaning

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we don't want to try and hit the database with invalid data before we know if this data is admissible

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or not.

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So we want to add certain rules to our forms such that before the user is able to actually submit this

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information we can ensure that everything matches a certain standard to kick things off we'll take a

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look at our freight action in our course controller.

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As you can see I'm already in debug mode but we want to take a look at what happens when we submit data.

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So we have our create action which renders our form for free courses.

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I'm just going to bring that up quickly.

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We click on courses and then we click Create New which then renders our free view and then we ask the

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user what is the title of this horse and how many credits should it be.

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This is a number and I shouldn't be able to put in text those kinds of things matter when you want to

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validate the information coming back.

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If you take a look at what happens upon the post you see that it checks if model state is valid which

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means it is assessing all of the information that's it just got from the user and see is this information

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valid.

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What we're going to do in this video is set up our own set of validations so that this automatically

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assesses our rules and makes a decision based on that.

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But before we do that we're going to take a look at the database and we're going to take a look at what

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happens when we try to submit information.

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If we take a look at the course table which I already have over here and look at the designer to see

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that both title and credit columns are designed to low no values which in fairness is probably not the

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best thing to do because then it allows me to create a course with no title and no credits which doesn't

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really make sense.

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It hits my breakpoint on this continuum and it goes ahead and it actually creates that empty record

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with no value for a title and no value for credits and there is nothing there which is something that

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we really do not want a user to be able to do.

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So the first step would be to change the validation rules or change the data type rules on our database

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so we can head back over to visual studio bringing up our designer for our course database and we say

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we want to not alone knows.

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So we take those alone those and then we can pick up eight then we say OK it's obvious this is going

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to give us an error as you see on here because then we're sitting on our database to not accept those.

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Well we have no values that exist.

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So I distance to remove that no record.

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And since I have my code operation I just do it here since my code works.

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So I delete this record and I want to delete it.

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And once again we hit a very point.

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I'm just going to continue and there it is removed.

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So now we can retry our save.

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So I keep a bit of data again and then it is successful this time no less a strand had a course with

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no title and no credits once again.

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So we are going to leave these blank because we want to test if changing the know setting and the rules

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that govern our data types in our database will be effective enough in setting up validations here.

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So when we click creates we see that it actually hits an error it hits an exception saying that something

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happened while trying to execute this.

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And if you scroll down and read the details it says as a we cannot insert a no value into column type.

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So we see that some amount of validation is actually occurring here.

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But this is probably not the best because you don't want your application to actually pause like this

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when a user is using it or give these kinds of errors that a user may not necessarily understand.

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So effective continue then you see that the page precedes the load and very nasty looking error that

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the typical user may not necessarily know how to process and may not want to see at all.

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So we're going to have to modify this behavior a bit.

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So I'm going to quickly exit debug mode and then we will get to work

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know in order to actually add these validation rules.

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We have to use some C sharp classes and not some o p type implementations to have a very fluid and somewhat

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disjointed but unified solution and that sounds like a paradox.

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But as I go through it you appreciate what I'm saying.

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So the first thing we want to do is to take a look at our model.

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So we said that we want to start adding validations to our courses.

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So we draw a line into our models folder into our EDL mix diagram and then we drill down into our model

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T T and look at our course class we need to appreciate what is here and do recall that each field that

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is outlined here is synonymous with what is in the database.

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So the fact that we see here that credit is to a notable value.

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He's a we of Visit our database but we did not update our models.

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So that is the first step we need to take.

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So we vote for the mix diagram and then we right click in open space and click update from database

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he will to refresh tray tables and take finish.

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This then reloads our tables and since the last time we were here I added middle name and date of birth

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to our student club.

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Now do remember that each time we refresh or do meet a change of any sort to our diagram we need to

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build so you can either go to build and click the solution or hold down control shift and B and that

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will actually effect a build operation.

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So I'm going to do that control shift and the mind is already built.

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So when we go to our course that cease fire we will see that it is updated to show that it is no longer

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a noticeable value a test to have an INT.

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And the tests have a string and the test of an integer here.

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So you can see that this change has been made successfully.

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So that's a step one for validation making sure that our database reflects our ambitions.

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Step two to our validation is to create what we call meta data.

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Classes are already feeling the needs and means that we have to you call meta data which is pretty much

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data about data.

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So in this case we have data in the form of our model or our class or our database tables and the data

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about that would be descriptions that we want.

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And in this case the descriptions we want would be our validation rules.

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OK.

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So what we want to do at this juncture is to create some classes that would describe rules that will

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govern our values here.

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Now since the work we're able to do concerns models and the best place to go ahead and create the fires

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that we need would be in the models folder.

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But then if you look in the models folder you see that you already have a kind of variety at least if

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you created the project in the way that I did with the individual user codes set up at the start then

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you would have these view models already existing.

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So in order to not mix and maintain that separation of concerns I'm just going to create a new folder

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and I'm going to call it meta classes

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and then inside amateur classes then I will have those meta data classes that I alluded to just not

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the first one I create of course is one for courses so right click click Add create a class and I will

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call this one courses meta data God and then that will give me this empty class.

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No.

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My first objective is to meet this empty class Miro.

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My actual models so I can go back to my course that see us fail and find all of these properties that

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are there for me.

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I don't have to bring over I don't have to validate its course I did.

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Because upon creation or ADR any operation we don't need to validate what the value is here.

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What we may want to restrict any course title to a length of 50.

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And we would want people putting in 50 credits for any course that they're creating maybe the maximum

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number of critics that any course can BES 8.

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So we're just going to copy these two over to them in our meta data class

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and then proceed to add or validations before we move on.

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In order to add our validations or what we call data annotations we have to include our library that

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gives us that function.

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So we'll see using system lots components model dots data notations.

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Now you may not remember this but then when you see the pattern that I am able to use visual studio

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will actually recognize this pattern and see to you that hey this is illegal.

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You have to include this library to use this and then they would proceed to suggest that you include

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that library.

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So like I said the first thing I want to do is include a string length of 50.

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So literally I'm going to say string length and there and so the sense finishes it for us.

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And I'm going to see 50 0 if I remove this and notice that it has no come to life.

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Everybody else is sort of somewhat green notes but this one is actually bold white text.

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If I removed this then typing this would cause an error in Visual Studio and then they would suggest

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to me that I need that library so you can always start typing it before and then include the library

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retroactively.

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Or you can just include this library and then you have no problem moving forward.

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I also said that for my integer I want to restrict the range of values to me from one.

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So that means you can't of course with zero credits and it should never pass hate

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no.

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It is.

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Where are the off nodes that you can actually include these directly on your course.

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That's you.

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So you didn't have to necessarily go and create a whole new file a whole new folder and the whole new

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file and then start from scratch and look those there you could actually put them right here above title

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and both credits the downsides of this however is that each time the model gets generated or regenerated

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or dated or change and you build your project then you're actually going to have this cease fire as

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well with as every other one listed here refreshed.

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So any changes that you made to it will be discarded.

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So you really don't want to do that because that would lead to a lot of rework and you have to do this

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each time.

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So I am suggesting that you create this new file and then you associate it with that model using a partial

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class and that we you have that.

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As I said disjointed because they're actually different files but unified because they're making reference

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to each other so it doesn't matter what happens here.

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Even if the courses table ceases to exist these courses and metadata of course this table will not in

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any way encroach on the operation of your system.

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So next we're going to create actually another class and in C sharp you can actually use one cease fire

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as a whole as many classes.

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Some people say it's bad practice some people practice it it's up to you you can decide what you want

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to do.

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I'm just going to use this one C.S. Das called meta courses method data and I'm just going to create

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another public class but this one will be partial public partial class and I'm going to give it the

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same name as the model that I wanted to be associated with.

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So that's one of those great bull P tricks where I can create.

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Sorry the name of the class is course I can create a partial class and give it some properties and it

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will work in conjunction with our original class.

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What I wanted to do however is be associated with the meta data class so I'll use another data notation

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and I see a meta data type and this is some fun C C sharp that's going to happen here but you can study

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this pattern or just know how to do it when the time is right.

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So I want to associate it with courses meta data so at the end of this exercise you would have created

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a meta data class which would have data notations that will govern the validations of your fields and

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you would have associated with the class coming from your model just in a very indirect and or P like

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we know.

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One final change before we move on and this is very very very important and it's a common mistake that

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people would run into trying to maintain that separation of concerns but the partial class that you

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defined needs to be in the same namespace as the class it is.

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Well let's say pirates off.

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So if I go to courses and I look at the namespace I see that it is in school and management but models.

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If we look at where the namespace is for the partial classes see that is in modules thought classes.

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So each folder determines that namespace hierarchy.

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Right.

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So we're going from the project school management tool folder called models so school management to

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a folder called models of a folder called Method classes and that is its namespace.

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So what we want to do is remove the metal thousands from the namespace.

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We can leave it physically in the folder but the namespace associated with this folder and any other

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file in that folder.

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So by doing so we are putting or partial class on priority.

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The hierarchical sense with its original counterparts so we can go ahead and actually debug and see

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if our validation works hard again.

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So we will look at the courses section and just run some tests to see if our validations are working.

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So we go to create new and then firstly we're going to just click Create so they expectation is that

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once invalid data is being sent across it will re both our attempts to create the record and this be

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an error message.

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So we create and without filling anything in.

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We see that the pages of three loads with an error message the credits field is required.

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We can quickly review where that error message is coming from.

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I'm bringing up visual studio still in debug mode and I am just going to go over to our view for create

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and courses and then we can just take a look at what is happening in the credits section of the form.

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So remember we have that label which gives us the word credits and then we have the edit which gives

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us our textbooks but then read underneath that we actually have an issue him a helper that is sending

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back a validation message right.

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And we see that the bootstrap class takes that danger is being applied.

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So that is basically seeing that once I try to submit and I'm just going to go to my controller real

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quickly and put a breakpoint right at this decision.

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So he creates and it hits that breakpoint and then it evaluates if the model's state is valid and you

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see that this is evaluating the Falls unlike all the other times in the previous examples where it validated

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and which is true.

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So if this validates the true then that should happen the fact that it goes to falls means that it will

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just return the same view which is our create view and it will return whatever data was being submitted.

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We know that we didn't try to submit anything.

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So everything comes back as null and zero and then that is what triggers the display of or validation

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message.

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So if I put in a title and you can see that I was testing this thing.

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So I put in a title with clearly more than 50 ages and do recall that our validation rule for courses

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C is that we should only accept 50 or up to 50.

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So if I take create it hits it again and it says that this state is not valid so it returns a view with

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the data we see we get back our data alongside a displayed error message that we are exceeding or maximum.

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And if I see a 10 critic course once again recall that or validation rule said one 2 eight.

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So that means anything less than one and anything more than eight will trigger an error message.

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So if I create once again it's our breakpoints the model validity is false.

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So we continue and it will display an appropriate error message displaying to the user hey your data

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is wrong for this reason.

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And so this is a pretty cool feature that we can use to ensure that our users are staying within the

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confines of what we expect for our data.

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So I can create a legitimate course is the Mets and D.C. by Asian and that could be one credit course

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and then I create.

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And then we see it hits our breakpoints and this time everything is valid and because it is valid it

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will go ahead and edit and see the changes and then redirect to our listing of courses.

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So I press on to the expectation is fulfilled.

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There we have our brand new course.

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So that's it so you can go about setting validations on your fields no data annotations actually serve

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a greater purpose than just setting validation rules they can actually influence what is displayed for

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a farm or for a value in that display name for helper function.

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So I understand to jump over to your studio real quickly and show you what I mean.

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Do recall that we have the label for and then in our e Thales view we do have display name for.

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So you can actually use data annotation to influence these.

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The simple way to change this would be to erase it and rewrite what you once the downsides of that is

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if the field changes or something abodes the what should be displayed changes and you have it sets at

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different points off your project then you're going to have to manually go through and change it as

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all those points which can be tedious if you however continue to use the HMO function and then you use

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your data annotation then once you meet the change in the data annotation it will be made right across

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your application.

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So just as a quick example for or courses form we have title and credits just like the fields are in

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our database.

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All right title and credits.

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So as they appear in our database that's how they get created in our module title credits and that is

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what will be displayed in our label for on our page title and credits those details.

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This year title and credits.

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No it seems in a sense and it seems unimportant for our courses because we only have one word.

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Well what about the case of students where we are actually collecting first name last name enrollment

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age and other things so you can see here that the last name is appearing as it does in the database

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with no space no discernible space here for human readability.

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If we keep details we see everything above the students.

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And once again this is not very human readable or friendly.

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Now when we go to students online courses we don't have only one word but we have two words.

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So we click on students and we see that we have the last name first name and enrollment date with no

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discernible space in between these names and labels.

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And that is not very user friendly.

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That's not good.

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We want to make sure that our users look at our screen and feel comfortable absorbing and digesting

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our information.

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And if I go to details Izzy it is a very similar situation.

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So we're going to have to use some data annotation to clean this up and make our students much more

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user friendly to when we're reading the information.

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So back in Visual Studio we want to do is create two classes to associates with students.

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One for our metadata and the one for all where parts of us and to recall that I created this older here

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method classes or it's a visa but we subsequently need to change the name space so that everything flows

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smoothly.

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Someone's rightly had lots of class and we're creating students into data and then the easy way to go

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about doing this is just to copy all of the fields that are coming back from our original module in

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our database so we drill down into the EDL mix file we find students that see us and then we can copy

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across all of these know notes once again that these things are no levels.

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So for your own purpose you may go ahead and change a database of data your model.

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But I really just need to give the data annotations here for student meta data so I copy those across

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and we want to run some custom labels for all of these needs of these fields.

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The first one I'm going to do is last name and I'm going to see string length and I'm just going to

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set up a validation I don't want anybody entering a string length of more than 50 for our last name.

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So I'm setting up a validation right here and you see the arrows being displayed and Visual Studio is

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telling me I need to include this library in orbit.

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So I use this function.

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Secondly I want to see that the display

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needs to have a name and I'm going to set a custom string and you can always pay attention to the tool

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tips they're always guiding you as to what values can go in.

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We want a name which is what is going to be displayed in the UI.

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You can just read that description and ascertain what it is and I want to display in the UI a last space

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name all right.

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So we're moving away from last name as one perceivable word to two words and I can just reuse these

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annotations for the first name.

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I don't want more than 50 and first name just puts in space to make it look more beautiful enrollment

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date.

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Well I don't need to specify a length because this is a date.

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The data type is already set.

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It's an a low doesn't know anyway.

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And I want to display enrollments date with a space or better yet it seems the top of it date of Rome

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and so rewarding it just to show you that it's not a matter of or just putting a space in there you

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can labile to whatever you want on your form.

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All right.

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And let me just do the same for a middle name so middle name I'm limiting the number of characters sitting

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on middle space.

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Name and date of birth would have similar rules for enrollment dates and surplus IDs anyway so this

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date of birth and then the second step of this entire transformation process is to create a public plus

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a partial plus and call it student and associate the Metro data class with it.

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And you can look back at the previous school was understands and type it here into a data type and then

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in brackets we see it type of sorry type off and then we spell out that it should be off type student

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meta data.

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And as our final act which probably could have come first anyway we want to make sure that our namespace

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is the same as the namespace for our part.

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So Target class and then having done all of this we can go ahead and continue with our development or

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in debug and see if everything clicks.

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Now when our students page loads you can start seeing the differences already you see that discernible

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space between the last name first name date of enrolments.

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So the labels have changed.

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If we go to create news see that the labels for the form have changed the middle name dates of enrollment

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will ever include the dates of birth on the create page as yet details so everywhere and that is dynamically

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using that each time a helper that we pointed out is in details display name for or in the create we

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have label for or in our index.

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Next we have display name for everywhere that you have something like that by setting up or data annotations

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and setting up our method class.

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We will see the different labels that we set being displayed for our users and that is indeed and in

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fact how you go about customizing what is displayed without being too intrusive.

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And by leveraging the flexibility that this framework gives you.