C# - Default Parameter Value

Default Value for Parameters in C#

In C#, default parameters (also called optional parameters) allow you to define parameters that do not require a value to be passed when the method is called. These parameters have default values that are used when no argument is provided for them. This feature enables you to call methods with fewer arguments and simplifies the method signature.

Default Parameters in C#

When you define a method, you can specify a default value for one or more parameters. If the caller does not provide an argument for that parameter, the default value is used.

Syntax

returnType MethodName(type param1 = defaultValue, type param2 = defaultValue)
{
    // Method body
}

defaultValue is the value that will be used if no argument is provided for that parameter when the method is called.

Example

using System;

class Calculator
{
    // Method with default parameters
    public void Add(int x, int y = 5)
    {
        Console.WriteLine($"The result of adding {x} and {y} is: {x + y}");
    }
}

class Program
{
    static void Main()
    {
        Calculator calc = new Calculator();

        // Calling with both arguments
        calc.Add(10, 15);  // Output: The result of adding 10 and 15 is: 25

        // Calling with only one argument, using default value for y
        calc.Add(10);      // Output: The result of adding 10 and 5 is: 15
    }
}

Explanation:

• The Add method has a default value of 5 for the second parameter y.
• When we call calc.Add(10, 15), both parameters are provided, so no default value is used.
• When we call calc.Add(10), only the first parameter x is passed, and the default value 5 is used for y.

Use Case for Default Parameters

User Preferences: Consider a method that displays a message. You might want the method to have a default color for the text, but you also want the ability to change the color if needed.

public void DisplayMessage(string message, string color = "blue")
{
    Console.ForegroundColor = (ConsoleColor)Enum.Parse(typeof(ConsoleColor), color, true);
    Console.WriteLine(message);
    Console.ResetColor();
}

Usage

// Using the default color (blue)
DisplayMessage("Hello World!");

// Using a custom color
DisplayMessage("Warning!", "Red");

Advantages of Default Parameters

• Code Simplification: Default parameters allow you to create methods that can be called with fewer arguments, reducing the need for method overloads.
• Flexible Method Signatures: You can write more flexible methods where some arguments are optional, which is useful when you want to provide default behavior for common use cases.