C# Error CS0641 – Attribute ‘{0}’ is only valid on classes derived from System.Attribute

C# Error

CS0641 – Attribute ‘{0}’ is only valid on classes derived from System.Attribute

Reason for the Error & Solution

‘attribute’ : attribute is only valid on classes derived from System.Attribute

An attribute was used that can only be used on a class that derives from System.Attribute.

The following sample generates CS0641:

// CS0641.cs  
using System;  
  
[AttributeUsage(AttributeTargets.All)]  
public class NonAttrClass   // CS0641  
// try the following line instead  
// public class NonAttrClass : Attribute  
{  
}  
  
class MyClass  
{  
   public static void Main()  
   {  
   }  
}