Attributed Programming in .NET Using C#

What does exactly happen to our custom attribute when the compiler compiles the class User? The simple explanation goes like this: when the compiler encounters the ValidLength specification in class User, it looks for a class ValidLength but it can find one. It then searches for a class ValidLengthAttribute and it finds one. Next, the compiler verifies if the target of ValidLengthAttribute is valid. It then verifies if there is a constructor whose signature matches the parameters used in the attribute specification. If a named parameter is used, it also verifies the existence of field or property by that name. The compiler also verifies if it is able to create an object of ValidLengthAttribute class. If no error is encountered, the attribute parameter values are stored along with other metadata information of the class.