Extending the MVC RequiredAttribute

Question

I have an extended class of RequiredAttribute that doesn't send error messages back. If I check it in the debugger the text is there alright.

public class VierRequired : RequiredAttribute
{
    public VierRequired(string controlName)
    {
        //...
    }

    public string VierErrorMessage
    {
        get { return ErrorMessage; }
        set { ErrorMessage = value; }
    }

    // validate true if there is any data at all in the object
    public override bool IsValid(object value)
    {
        if (value != null && !string.IsNullOrEmpty(value.ToString()))
            return true;

        return false; // base.IsValid(value);
    }
}

I call it like this

[VierRequired("FirstName", VierErrorMessage = "Please enter your first name")]
public string FirstName { get; set; }

And the mvc-view

<%: Html.TextBoxFor(model => model.FirstName, new { @class = "formField textBox" })%>
<%: Html.ValidationMessageFor(model => model.FirstName)%>

It works if I use the normal Required annotation

[Required(ErrorMessage = "Please enter your name")]
public string FirstName { get; set; }

But the custom does not send any error message back

Well, for one thing, your constructor doesn't have the same name as your class. Was that just a transcription error? — Ann L., Sep 24 '12 at 21:48
@Benjamin The error messages doesn't seem to be returned to the view. But if I use normal Required annotation they do. — Eric Herlitz, Sep 24 '12 at 21:57
I'm skeptical `value.ToString()` is actually doing what you think it is. You need `value as String` instead. — Erik Funkenbusch, Sep 24 '12 at 22:10

Benjamin Gale · Accepted Answer · 2013-04-23T10:47:26.960

I also had a problem with client side validation when I created my own derivative of the RequiredAttribute. To fix it you need to register your data annotation like so:

DataAnnotationsModelValidatorProvider.RegisterAdapter(
            typeof(VierRequired),
            typeof(RequiredAttributeAdapter));

Simply call this in your Application_Start() method and client side validation should work as normal.

If your attribute is not working when you are POST-ing your form then this would indicate to me that there is something wrong with the logic in your attribute (check you IsValid method). I am also not sure what you are trying to achieve with your derived data annotation; your logic looks like it is trying to do pretty much what the default attribute does anyway:

Taken from the MSDN documentation:

A validation exception is raised if the property is null, contains an empty string (""), or contains only white-space characters.

Turns out this was correct, my setup is somewhat complex since I run the mvc project inside another project. — Eric Herlitz, Sep 27 '12 at 08:40

Extending the MVC RequiredAttribute

1 Answers1

Linked