C# ref parameter
Description
Passing variables by value is the default, but you can force value parameters to be passed by reference.
To pass by reference , C# provides the ref parameter modifier.
Syntax
methodName(ref type parameterName){
}
when calling the method:
methodName(ref variableName);
Notice how the ref modifier is required both when writing and when calling the method. This makes it very clear what's going on.
Example 1
Example for ref parameter
using System;/*w ww .j a va2 s .c o m*/
class MainClass
{
static void Main(string[] args)
{
int MyInt = 5;
MyMethodRef(ref MyInt);
Console.WriteLine(MyInt);
}
static public int MyMethodRef(ref int myInt)
{
myInt = myInt + myInt;
return myInt;
}
}
The code above generates the following result.
Example 2
The ref modifier is essential in implementing a swap method:
using System;// w ww . j a va 2 s .c o m
class Test
{
static void Swap (ref string a, ref string b)
{
string temp = a;
a = b;
b = temp;
}
static void Main()
{
string x = "Penn";
string y = "Teller";
Swap (ref x, ref y);
Console.WriteLine (x); // Teller
Console.WriteLine (y); // Penn
}
}
The code above generates the following result.
Note
A parameter can be passed by reference or by value, regardless of whether the parameter type is a reference type or a value type.
Example 3
We can use ref modifier for reference type value as well.
using System;//from www . jav a 2s . co m
class Rectangle
{
public int Width = 5;
public int Height = 5;
}
class Program
{
static void change(ref Rectangle r)
{
r = null;
}
static void Main(string[] args)
{
Rectangle r = new Rectangle();
Console.WriteLine(r.Width);
change(ref r);
Console.WriteLine(r == null);
}
}
The output:
If we use the ref modifier in front of a reference
type what we get in the method is the address of the reference or
the reference of the reference.