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);
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 Tester { static void Main( ) { Tester t = new Tester( ); t.DisplayVals(5, 6, 7, 8); int[] explicitArray = new int[] { 1, 2, 3, 4, 5 }; t.DisplayVals(explicitArray); } public void DisplayVals(params int[] intVals) { foreach (int i in intVals) { Console.WriteLine("DisplayVals {0}", i); } } } }
The output looks like this:
DisplayVals 5 DisplayVals 6 DisplayVals 7 DisplayVals 8 DisplayVals 1 DisplayVals 2 DisplayVals 3 DisplayVals 4 DisplayVals 5