What Does the `new` Keyword Mean in a C# Method Signature?

Understanding the new Keyword in Method Signatures

While refactoring code, an unusual method signature emerged:

private static new MyObject CreateSomething()
{
  return new MyObject{"Something New"};
}

Question: What is the significance of the new keyword in this method signature? Is it a feature introduced in C# 3.0? How does it differ from override?

Answer:

The new keyword in a method signature serves a distinct purpose from override. According to Microsoft's MSDN documentation, it allows for hiding inherited members.

An example illustrating the difference:

public class A
{
   public virtual void One();
   public void Two();
}

public class B : A
{
   public override void One();
   public new void Two();
}

B b = new B();
A a = b as A;

a.One(); // Calls implementation in B
a.Two(); // Calls implementation in A
b.One(); // Calls implementation in B
b.Two(); // Calls implementation in B

In this example, override is used on the One method to override its implementation in the base class A. On the other hand, new is used on the Two method to hide the inherited implementation from A.

Key Difference:

override modifies virtual or abstract methods to provide different implementations in derived classes. In contrast, new hides inherited members, both virtual and non-virtual, allowing for new implementations to be provided in derived classes.

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