Parameters  are variables that are passed into a function which defines how something should be done. The values which are passed into the function are known as arguments.

There are five methods of passing the parameter:-

• Value type
• Reference type
• Output type
• Optional parameter
• Named parameter

1. Value type- In value type parameter there is no need to give any keyword while passing the parameters.

e.g of value type parameter:

using System;
 
namespace Value_Type
{
  class Program
   {
     public static int square(int num)
      {
        return num * num;
      }
     static void Main(string[] args)
      {
        int val,number;
        number = 5;
        //Passing the copy value of number variable
        val = Program.square(number);
        Console.Write(val);
        Console.ReadLine();
      }
   }
}

2. Reference type- In reference type variable we need to provide the ref keyword with a parameter. In ref type the variable needs to be initialized before use.

e.g of ref type parameter:

class Refeg 
 { 
   static void Method(ref int i)
    { 
        // Rest the mouse pointer over i to verify that it is an int.
        // The following statement would cause a compiler error if i 
       // were boxed as an object. 
          i = i + 44;
    }

    static void Main() 
      { 
         int val = 1; Method(ref val); 
         Console.WriteLine(val);


            // Output: 45 
       } 
}

3. Output type- Output type parameter are declared by providing out keyword. In out type parameter both method calling and definition must use the out keyword.

e.g of out type parameter is:

class OutEg 
{
 static void Method(out int i)
 { 
     i = 44;  
 }
  static void Main()
   { 
     int value; 
     Method(out value);
     // value is now 44
   } 
}

4. Optional parameter- It is new parameter introduced in c#. It allows us to neglect the predefined values.

e.g of optional parameter:

public int Sum(int a, int b, int c = 0, int d = 0); 
/* c and d is optional */
 Sum(10, 20); //10 + 20 + 0 + 0 
 Sum(10, 20, 30); //10 + 20 + 30 + 0 
 Sum(10, 20, 30, 40); //10 + 20 + 30 + 40

5.Named parameter- In this arguments are passed by name rather than value. This is also a new parameter introduced in c#.

e.g of named parameter:

public void CreateAccount(string name, string address = "unknown", int age = 0); CreateAccount("Sara", age: 30);
CreateAccount(address: "India", name: "Sara");