C# Default Parameters

Summary: in this tutorial, you’ll learn how to use the C# default parameters to simplify the function call.

Introduction to the C# default parameters

When defining a function with parameters, you can specify the default arguments like this:

<modifiers> <return-type> functionName(parameter1,parameter2=argument2,...)Code language: C# (cs)

C# requires that the parameters with default arguments appear after other parameters.

The following example defines a function calculateTax() that calculates the net price based on the selling price and sales tax:

double calculatePrice(double sellingPrice, double salesTax=0.08)
{
    return sellingPrice * (1 + salesTax);
}Code language: C# (cs)

In this example, the salesTax parameter has a default value of 0.08.

When calling the function, if you don’t specify the argument for the parameter with default arguments, the function will take the default argument instead.

For example:

double calculatePrice(double sellingPrice, double salesTax=0.08)
{
    return sellingPrice * (1 + salesTax);
}

var netPrice = calculatePrice(100);

Console.WriteLine($"The net price is {netPrice:0.##}");Code language: C# (cs)

Output:

108Code language: C# (cs)

In this example, we only pass the selling price to the calculatePrice() function. Therefore, the calculatePrice() function will use 0.08 for the salesTax parameter. As a result, the net price is 108.

If you pass the salesTax argument, the function will use that value instead of the default argument. For example:

double calculatePrice(double sellingPrice, double salesTax=0.08)
{
    return sellingPrice * (1 + salesTax);
}

var netPrice = calculatePrice(100,0.1);

Console.WriteLine($"The net price is {netPrice:0.##}");Code language: C# (cs)

Output:

110Code language: C# (cs)

In this example, we pass the salesTax as 0.1 to the calculatePrice() function. Hence, the function uses 0.1 instead of 0.08 for the salesTax parameter.

Summary

Use function default parameters to simplify the function call
Place the parameters with default values after other parameters.

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