Compiler Error CS0549

'function' is a new virtual member in sealed class 'class'

A sealedclass cannot be used as a base class. Therefore, it is useless to have a virtual method in sealed class.

The following sample generates CS0549:

// CS0549.cs  
// compile with: /target:library  
sealed public class MyClass  
{  
   virtual public void TestMethod() {}   // CS0549  
   public void TestMethod2() {}   // OK  
}