How to Fix C# Error: Only assignment, call, increment, decrement, and new object expressions can be used as a statement

I was trying to compile the below code while i got the error. basically this error occur when you try to use a keyword as statement. you should make it statement for example in below code i have null as statement either you should assign null in a variable or write a statement. only null is not an statement.

to remove error replace

  null;

to

str3 = null;

Now compile it will work.

C# Program With Error:

using System;

namespace MyApp
{
    class my_class
    {
        static void Main(string[] args)
        {
            String str1 = "SoftwareTestingNet.com";
            String str2 = "TestingWiz.com";
            String str3;

            if (str1 == str2)
            {
                Console.WriteLine("Equal.");
            }
            else
            {
                null;
            }                  

            Console.ReadLine();
        }       
    }
}