Compiler Warning (level 3) CS0067

The event 'event' is never used

An event was declared but never used in the class in which it was declared.

The following sample generates CS0067:

// CS0067.cs  
// compile with: /W:3  
using System;  
delegate void MyDelegate();  
  
class MyClass  
{  
   public event MyDelegate evt;   // CS0067  
   // uncomment TestMethod to resolve this CS0067  
/*  
   private void TestMethod()  
   {  
      if (evt != null)  
         evt();  
   }  
*/  
   public static void Main()  
   {  
   }  
}  

If the event is unused intentionally, for example, when it's part of an interface implementation, then you can avoid emitting an unnecessary field as follows:

using System;  
  
public interface IThing  
{  
   event Action? E;  
}  
  
public class Thing : IThing  
{  
   // no CS0067 though the event is left unused  
   public event Action? E { add { } remove { } }  
}