If a class have multiple methods by same name but different parameters, it is known as Method Overloading.

string sum(int A)
string sum(int A, int B)

C# no need to use any keyword while overloading a method either in same class or in derived class.

While overloading methods, a rule to follow is the overloaded methods must differ either in number of arguments they take or the data type of at least one argument.

Example

using System;
namespace MethodOverloading
{
    class Class1
    {
        public int Sum(int A, int B)
        {
            return A + B;
        }
        public float Sum(int A, float B)
        {
            return A + B;
        }
    }
    class MainClass
    {
        static void Main()
        {
            Class1 obj = new Class1();
            Console.WriteLine(obj.Sum(20, 30));
            Console.WriteLine(obj.Sum(20, 15.70f));
            Console.Read();
        }
    }
}

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