Why can't I use resources as ErrorMessage with DataAnnotations?

Asked 2010-04-22T07:17:58.287

Why can't I do like this?

[Required(ErrorMessage = "*")]
[RegularExpression("^[a-zA-Z0-9_]*$", ErrorMessage = Resources.RegistrationModel.UsernameError)]
public string Username { get; set; }

What is the error message telling me?

An attribute argument must be a constant expression , typeof expression or array creation expression of an attribute parameter type.

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1 Answer

It means that you cannot determine the value of the argument you are passing into the attribute at runtime, it must be at compile time so the value is embedded into the assembly.

The error message value needs to be a constant expression.

For information, attribute arguments can only be of types bool, byte, char, short, int, long, float, double, string, System.Type, and enums.

answered 2010-04-22T07:27:07.867

Why can't I use resources as ErrorMessage with DataAnnotations?

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