C＃可执行属性

Question

Is any way to define attribute like:

public class MyAttribute : Attribute
{
    void OnFunctionInvoke() { ... }
}

And mark some function with that attribute

[MyAttribute]
void SomeFunction() { ... }

When SomeFunction is invoked i want OnFunctionInvoke() to be invoked before.

Answer 1

You can try using CodeAccessSecurityAttribute as a by-way :

https://msdn.microsoft.com/en-us/library/system.security.permissions.codeaccesssecurityattribute(v=vs.110).aspx

  using System.Security.Permissions;
  ...

  [AttributeUsage(AttributeTargets.All)]
  public class MyInterceptAttribute: CodeAccessSecurityAttribute {
    public MyInterceptAttribute(SecurityAction action)
      : base(action) {
    }

    public override System.Security.IPermission CreatePermission() {
      //TODO: put relevant code here
      Console.Write("Before method execution!");

      return null;
    }
  }

  ...

  // We demand permissions which in turn leads to CreatePermission() call    
  [MyInterceptAttribute(SecurityAction.Demand)]  
  public void MyMethodUnderTest() {
    Console.Write("Method execution!");
  }

So it's, technically, possible (we exploit security), but it's a by-way only.

Answer 2

Natively, there's no way to do that. However, AOP frameworks like PostSharp will let you do that kind of thing.

Answer 3

As Thomas levesque wrote, it is not possible.

Alternative you can considerate using Decorator design pattern.