Default arguments

In C#, you can define methods with default parameters. This means that when you call the method, you can choose to omit some arguments, and the method will use the default values you specified instead.

In more simple terms - we don’t need to provide values for all parameters when calling a method if some of them have default values.

Syntax

You can specify default values for parameters in the method definition by using the = operator followed by the default value. For example:

static void Greet(string name = "Guest", string greeting = "Hello")
{
    Console.WriteLine(greeting + ", " + name + "!");
}

Now, we can call the Greet method in several ways:

Greet("Alice", "Hi"); // the normal way
Greet("Bob");         // uses default greeting
Greet();              // uses default name and greeting

The output of the above calls will be:

Hi, Alice!
Hello, Bob!
Hello, Guest!

Default arguments before specified arguments

In the example above, we can’t easily call Greet with a custom greeting but the default name. That’s because C# will assume we’re providing the first argument of type string, which is name.

To work around this, we can use named arguments to specify which parameter we want to provide a value for:

Greet(greeting: "Welcome");
// default name, custom greeting

This will output:

Welcome, Guest!