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C# Method Parameters

A parameter is a variable named in a method definition. A call passes a value, called an argument, into the parameter.

One string parameter

Greet takes one string parameter. The call passes the name Hana as the argument.

using System;

class Program
{
    static void Greet(string name)
    {
        Console.WriteLine("Hello, " + name);
    }

    static void Main(string[] args)
    {
        Greet("Hana");
    }
}

Return a sum

Add takes two int parameters. The return word sends the sum back and Main prints it.

using System;

class Program
{
    static int Add(int a, int b)
    {
        return a + b;
    }

    static void Main(string[] args)
    {
        Console.WriteLine(Add(4, 5));
    }
}

Many values with params

Sum takes a params array of numbers. One call passes three values and the next call passes two values.

using System;

class Program
{
    static int Sum(params int[] numbers)
    {
        int total = 0;
        foreach (int num in numbers)
        {
            total += num;
        }
        return total;
    }

    static void Main(string[] args)
    {
        Console.WriteLine(Sum(1, 2, 3));
        Console.WriteLine(Sum(4, 5));
    }
}

Default parameter value

ShowLevel has a default value of Beginner. A call can leave the argument out or pass its own value.

using System;

class Program
{
    static void ShowLevel(string level = "Beginner")
    {
        Console.WriteLine("Level: " + level);
    }

    static void Main(string[] args)
    {
        ShowLevel();
        ShowLevel("Advanced");
    }
}

Example

using System;

class Program
{
    static double Total(double price, double tax)
    {
        return price + tax;
    }

    static void Main(string[] args)
    {
        double total = Total(50, 10);
        Console.WriteLine("Total: " + total);
    }
}

Key points

  • A parameter sits in parentheses after the method name.
  • An argument is the value a call passes for a parameter.
  • A method can take more than one parameter.
  • The return keyword sends a value back to the caller.
  • Use params before an array parameter to accept any count of values.
  • A default value is used when a call leaves the argument out.

In this example, Total takes a price and a tax amount. Main passes 50 and 10 as the arguments. The method returns 60 as a double value. Main stores the value in total, and the print line shows Total: 60.

Try it Yourself

Edit the code, then press Run.

Running is simulated · Programiz C# Compiler

Exercise

What does a default parameter value do?