C# - Passing Parameters by Output

A return statement can be used for returning only one value from a function. However, using output parameters, you can return two values from a function. Output parameters are like reference parameters, except that they transfer data out of the method rather than into it.

The following example illustrates this:

using System;

namespace CalculatorApplication
{
   class NumberManipulator
   {
      public void getValue(out int x )
      {
         int temp = 5;
         x = temp;
      }
   
      static void Main(string[] args)
      {
         NumberManipulator n = new NumberManipulator();
         /* local variable definition */
         int a = 100;
         
         Console.WriteLine("Before method call, value of a : {0}", a);
         
         /* calling a function to get the value */
         n.getValue(out a);

         Console.WriteLine("After method call, value of a : {0}", a);
         Console.ReadLine();

      }
   }
}

When the above code is compiled and executed, it produces following result:

Before method call, value of a : 100
After method call, value of a : 5

The variable supplied for the output parameter need not be assigned a value the method call. Output parameters are particularly useful when you need to return values from a method through the parameters without assigning an initial value to the parameter. Look at the following example, to understand this:

using System;

namespace CalculatorApplication
{
   class NumberManipulator
   {
      public void getValues(out int x, out int y )
      {
          Console.WriteLine("Enter the first value: ");
          x = Convert.ToInt32(Console.ReadLine());
          Console.WriteLine("Enter the second value: ");
          y = Convert.ToInt32(Console.ReadLine());
      }
   
      static void Main(string[] args)
      {
         NumberManipulator n = new NumberManipulator();
         /* local variable definition */
         int a , b;
         
         /* calling a function to get the values */
         n.getValues(out a, out b);

         Console.WriteLine("After method call, value of a : {0}", a);
         Console.WriteLine("After method call, value of b : {0}", b);
         Console.ReadLine();
      }
   }
}

When the above code is compiled and executed, it produces following result (depending upon the user input):

Enter the first value:
7
Enter the second value:
8
After method call, value of a : 7
After method call, value of b : 8