I have just noticed that DataTypeAttribute class is inherited from System.ComponentModel.DataAnnotations.ValidationAttribute.
In terms of ASP.NET MVC DefaultModelBinder class, is DataTypeAttribute is a validation attribute? In plain English, does ModelBinder validate the object according to DataTypeAttribute?
For example, if I specify DataType property to DataType.EmailAddress, will it validate the e-mail address or this attribute is only providing metadata for objects.
UPDATE
I found a similar question on SO :
Is the DataTypeAttribute validation working in MVC2?
So, according to that it is not working as a validation attribute. So, why it is inherited from System.ComponentModel.DataAnnotations.ValidationAttribute if it is not serving as a validation attribute?
DataTypeAttribute does not contain any validation logic itself.
The reason it derives from ValidationAttribute is so that you could create a new custom data type class, which was both a DataType and a Validation, all wrapped up into one. It's an unfortunate side-effect of .NET not allowing multiple inheritance.
So, yes, it's a validator... that does no validation by default. It's waiting patiently for you to do the heavy lifting. :)
Actually, if you look inside of MVC 3 Futures, you'll see that we leveraged this to create new custom validators where we knew that jQuery was already capable of providing client-side validation logic, and we added mirrored server-side validation logic (and preserved the DataType benefits for templating).
Based on the MVC3 source code the only purpose of the DataTypeAttribute is to populate the ModelMetadata.DataTypeName property .And this property is only used by the EditorFor/DisplayFor template generation. So you were right it has nothing to do with validation. So I don't know why is it inherited from ValidationAttribute. Maybe the framework authors reserved it for future use.
