Compiler Error CS0644

'class1' cannot derive from special class 'class2'

Classes cannot explicitly inherit from any of the following base classes:

  • System.Enum

  • System.ValueType

  • System.Delegate

  • System.Array

These are used as implicit base classes by the compiler. For example, System.ValueType is the implicit base class of structs.

The following sample generates CS0644:

// CS0644.cs  
class MyClass : System.ValueType   // CS0644