Custom Validation with IValidatableObject in MVC

In this post you will learn how to create a self validatable object using IValidatableObject to validate data in MVC.

Let’s look at a situation where we will implement IValidatableObject to enable date validation.

In the above form, you can see Date of Birth is in future which is wrong from every prospective. So to validate this date we can implement IValidatableObject, let’s see how.

Now, follow the steps from here.

Step 1

Open model and implement interface IValidatableObject. You can get this popup by pressing Ctrl+. (dot). It implements validatable interface automatically in Visual Studio.

When you click on ‘Implement interface ‘IValidatableObject’ you will have following interface. This will return IEnumerable<ValidationResult> by taking one parameter as ValidationContext.

Step 2

Now, inside above context we can implement our validation checks as given below.

In above self-validation context I have implemented two checks. First, is date in future? Second, is date in too past? If condition matches will return the validation result.

Step 3

Run the application and test it. It will work fine with two unavoidable bugs.

First, the newly added validation will only work when you click the button however it should immediately report the error if selected date is in future or too past.

Second, the validation error message should be displayed with the Date of Birth textbox.

Step 4

Actually by default every error message get placed here (in the image below) and this is the reason we are getting error message on the top.

Also, the reason of this error is that we didn’t associated the returned validation result with appropriate property in the model.

Step 5

To associate the model property with validation result, let’s make following changes.

Created a variable which will contain list of model properties because ValidationResult only accepts IEnumerable data (look at the intellisense in above image) and the reason is a ValidationResult can be applied to multiple model properties.

Now, if you run the application at this point you will see everything working. Awesome.

Note: Thanks to Joy (a reader of this blog entry) who commented right below to mention this. IValidatableObject method only be called when all the property validation has passed.

Hope this helps.