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Compiler Error CS0549

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

A sealed class 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