The out and the ref parameters are used to return values in the same variables that you pass as an argument of a method. These parameters are very useful when your method needs to return more than one value.
In this article, I will explain how to use these parameters in your C# applications.
The out Parameter
The out parameter can be used to return the value in the same variable passed as a parameter of the method. Any changes made to the parameter will be reflected in the variable.
public class mathClass
{
public static int TestOut(out int iVal1, out int iVal2)
{
iVal1 = 10;
iVal2 = 20;
return 0;
}
public static void Main()
{
int i, j; // variable need not be initialized
Console.WriteLine(TestOut(out i, out j));
Console.WriteLine(i);
Console.WriteLine(j);
}
}
The ref parameter
The ref keyword on a method parameter causes a method to refer to the same variable that was passed as an input parameter for the same method. If you do any changes to the variable, they will be reflected in the variable.
You can even use ref for mutiple method parameters.
static void Main(string[] args)
{
// Ref sample
int refi; // variable need not be initialized
refi = 3;
RefTest(ref refi);
Console.WriteLine(refi);
Console.ReadKey();
}
public static void RefTest(ref int iVal1)
{
iVal1 += 2;
}
Complete sample
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace RefOutSample
{
class Program
{
static void Main(string[] args)
{
// Out sample
int i, j; // variable need not be initialized
Console.WriteLine(TestOut(out i, out j));
Console.WriteLine(i);
Console.WriteLine(j);
// Ref sample
int refi; // variable need not be initialized
refi = 3;
RefTest(ref refi);
Console.WriteLine(refi);
Console.ReadKey();
}
public static int TestOut(out int iVal1, out int iVal2)
{
iVal1 = 10;
iVal2 = 20;
return 0;
}
public static void RefTest(ref int iVal1)
{
iVal1 += 2;
}
}
}