Learning C# 3.0

The params Keyword

One of the more unusual uses of arrays is the params keyword. If you have a method that accepts an array, the params keyword allows you to pass that method a variable number of parameters, instead of explicitly declaring the array. Of course, the parameters must all be of the same type. Because of the params keyword, the method will receive an array of that type.

In the next example, you create a method, DisplayVals( ), that takes a variable number of integer arguments:

public void DisplayVals(params int[] intVals)

Inside the method, you can iterate over the array as you would over any other array of integers:

foreach (int i in intVals)
{
   Console.WriteLine("DisplayVals {0}",i);
}

The calling method, however, need not explicitly create an array: it can simply pass in integers, and the compiler will assemble the parameters into an array for the DisplayVals( ) method:

t.DisplayVals(5,6,7,8);

You are also free to pass in an array if you prefer:

int [] explicitArray = new int[5] {1,2,3,4,5};
t.DisplayVals(explicitArray);

Warning

You can use only one params argument for each method you create, and the params argument must be the last argument in the method’s signature.

Example 10-4 illustrates using the params keyword.

Example 10-4. You can use the params keyword to pass a variable number of parameters to a method that accepts an array

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Example_10_4_ _ _ _params_keyword { public class ...