Compiler Error CS1722

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Base class 'class' must come before any interfaces

When specifying a class to inherit from and interfaces to implement, the class name must be specified first.

Example

The following sample generates CS1722.

// CS1722.cs
// compile with: /target:library
public class A {}
interface I {}

public class MyClass : I, A {}   // CS1722
public class MyClass2 : A, I {}   // OK