How to write nested classes in C#?

Nested classes are those classes that are contained in another class declarations. The below program in C# will demonstrate this

using System;
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {  
            OuterClass objOuterClass = new OuterClass();
            objOuterClass.SayHelloFromOuterClass();
            var innerClass = new OuterClass.InnerClass();
            innerClass.SayHelloFromInnerClass();
        }
    }
    class OuterClass
    {
        public void SayHelloFromOuterClass()
        {
            Console.WriteLine("Hello from Outer Class");
        }
        public class InnerClass
        {
            public void SayHelloFromInnerClass()
            {
                Console.WriteLine("Hello from Inner Class");
            }
        }
    }
}