Validating Enum Values within C# MVC. Partial validation occurs - How to change validation behaviour?

Question

I\'ve been representing an enum within my razor view as a hidden field, which is posted back to an action result.

I\'ve noticed that when it binds the string value p

Answer 1

Ok, so I've found out the answer to my own question.

The error message that appeared is more of a generic error message for when the binding wasn't possible. When the binding attempts to bind a non-existent string representation of the enum value posted from the HTML to the enum, it produces the error:

The value 'myincorrectvalue' is not valid for QuizType.

The exact same error message would appear if I were to attempt to bind a string value to an int within my View Model class.

It seems that the issue is that as well as the string representation, an enum can be any integer value. I can set the enum to any number, even if that number doesn't exist within my enum.

/// <summary>
/// Quiz Types Enum
/// </summary>
public enum QuizType
{
    /// <summary>
    /// Scored Quiz
    /// </summary>
    Scored = 0,

    /// <summary>
    /// Personality Type Quiz
    /// </summary>
    Personality = 1
}

Therefore, this is valid and will be bound without error to my enum value, even though 1000 doesn't exist within my enum:

<input data-val="true" id="QuizType" name="QuizType" type="hidden" value="1000">

//  Binder will bind this just fine
QuizType = 1000

That's where the EnumDataType validation attribute comes in. If I add the validation attribute to my enum within my view model:

[EnumDataType(typeof(QuizType), ErrorMessage = "Quiz type value doesn't exist within enum")]
public QuizType QuizType { get; set;}

With the attribute in place, I will only be able to assign my valid enum values (0 or 1 for this example).

So the incorrect STRING representations posted from the HTML is validated for you automatically upon binding, but a check for any integer value will not.

I hope that this clears up validating ENUMS within ASP.NET MVC.