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System.AttributeTargets.GenericParameter in C# : how do I use such an attribute?

In C#, when specifying how an attribute class should be used, there is a GenericParameter value in the System.AttributeTargets enum. How can we apply such an attribute, what is the syntax ?

[System.AttributeUsage(System.AttributeTargets
public sealed class MyAnnotationAttribute : System.Attribute {
    public string Param { get; private set; }
    public MyAnnotationAttribute(string param) { Param = param; }
}

Same question goes for other exotic attribute targets, like System.AttributeTargets.Module (I don't even know how to declare modules other than the main module???), System.AttributeTargets.Parameter and System.AttributeTargets.ReturnValue.

like image 595
Suzanne Soy Avatar asked May 23 '13 18:05

Suzanne Soy


1 Answers

// Assembly and module
[assembly: AttributesTest.MyAnnotation("Assembly")]

[module: AttributesTest.MyAnnotation("Module")]

namespace AttributesTest
{
    // The attribute
    [System.AttributeUsage(System.AttributeTargets.All, AllowMultiple = true)]
    public sealed class MyAnnotationAttribute : System.Attribute
    {
        public string Param { get; private set; }
        public MyAnnotationAttribute(string param) { Param = param; }
    }

    // Types
    [MyAnnotation("Class")]
    public class SomeClass { }

    [MyAnnotation("Delegate")]
    public delegate int SomeDelegate(string s, float f);

    [MyAnnotation("Enum")]
    public enum SomeEnum { ValueOne, ValueTwo }

    [MyAnnotation("Interface")]
    public interface SomeInterface { }

    [MyAnnotation("Struct")]
    public struct SomeStruct { }

    // Members
    public class MethodsExample
    {
        [MyAnnotation("Constructor")]
        public MethodsExample() { }

        [MyAnnotation("Method")]
        public int SomeMethod(short s) { return 42 + s; }

        [MyAnnotation("Field")]
        private int _someField;

        [MyAnnotation("Property")]
        public int SomeProperty {
            [MyAnnotation("Method")] get { return _someField; }
            [MyAnnotation("Method")] set { _someField = value; }
        }

        private SomeDelegate _backingField;

        [MyAnnotation("Event")]
        public event SomeDelegate SomeEvent {
            [MyAnnotation("Method")] add { _backingField += value; }
            [MyAnnotation("Method")] remove { _backingField -= value; }
        }
    }

    // Parameters
    public class ParametersExample<T1, [MyAnnotation("GenericParameter")]T2, T3>
    {
        public int SomeMethod([MyAnnotation("Parameter")]short s) { return 42 + s; }
    }

    // Return value
    public class ReturnValueExample
    {
        [return: MyAnnotation("ReturnValue")]
        public int SomeMethod(short s) {
            return 42 + s;
        }
    }
}
like image 71
Suzanne Soy Avatar answered Nov 09 '22 12:11

Suzanne Soy