test if a method is an override; i.e., it overrides the implementation of the same method in a base class

IsOverride.cs

using System.Reflection;
using NUnit.Framework;

public static class MethodInfoExtensions
{
    public static bool IsOverride(this MethodInfo m)
    {
        return m.GetBaseDefinition().DeclaringType != m.DeclaringType;
    }
}

public class IsOverrideTests
{

    class Base
    {
        public virtual void Overridden() { }
        public virtual void Inherited() { }
    }

    class Derived : Base
    {
        public override void Overridden() { }
    }

    [Test]
    public void Overriden()
    {
        Assert.IsTrue(typeof(Derived).GetMethod("Overridden").IsOverride());
    }

    [Test]
    public void Inherited()
    {
        Assert.IsFalse(typeof(Derived).GetMethod("Inherited").IsOverride());
    }

    interface Interface
    {
        void F();
    }

    class Implementation : Interface
    {
        public virtual void F() { }
    }

    [Test]
    public void InterfaceImplementation()
    {
        Assert.IsFalse(typeof(Implementation).GetMethod("F").IsOverride());
    }

    class NonVirtualBase
    {
        public void F() { }
    }

    class NonVirtualDerived : NonVirtualBase
    {
        public new void F() { }
    }

    [Test]
    public void MethodHiding()
    {
        Assert.IsFalse(typeof(NonVirtualDerived).GetMethod("F").IsOverride());
    }
}