Method Parameter

In this chapter you will learn:

What is method parameter
Pass int value to a function
Parameters are local

What is method parameter

The parameters define the input value for a method.

The following code defines a method called add, which adds two int type variables together.

add method has two parameters, a and b. When calling the add method we must provide data for a and b.

using System;/* j a va 2s.  co m*/

class Program
{
    static int add(int a, int b)
    {
        int result = a + b;
        Console.WriteLine(result);
        return result;
    }

    static void Main(string[] args)
    {
        add(1, 2);
    }
}

Pass int value to a function

using System;/* ja  v  a  2 s . c o m*/

class MainClass
{
   public static void Main() {
      int SomeInt = 6;
      
      int s = Sum(5, SomeInt);
      
      Console.WriteLine(s);        
   }
   public static int Sum(int x, int y)               // Declare the method.
   {
      return x + y;                                  // Return the sum.
   }
   
}

The code above generates the following result.

Parameters are local

using System;//from  j  av  a  2s .  c o  m


class Program
{
    static void change(int i)
    {
        i = i + 1;
        Console.WriteLine("in change method:" + i);
    }


    static void Main(string[] args)
    {
        int i = 2;

        change(i);

        Console.WriteLine("in main method:" + i);
    }
}

The output:

From the output we can see that changing the value in change method has no effect on the variable i in main method.

For reference type parameters the value of the reference is copied not the object itself.

The following code defines a class Rectangle. Class is a reference type. The change method accepts the Rectangle type as its parameter. In the change method new value is assigned to the parameter.

using System;/* j  a v  a  2s.com*/

class Rectangle
{
    public int Width = 5;
    public int Height = 5;

}

class Program
{
    static void change(Rectangle r)
    {
        r.Width = 10;
    }
    static void Main(string[] args)
    {
        Rectangle r = new Rectangle();
        Console.WriteLine(r.Width);
        change(r);
        Console.WriteLine(r.Width);
    }
}

The output:

We can see that the main method gets the changed value from change method. The change method changes the value from the reference.

To see the effect of a copied reference we can change the code above as follows.

using System;/*  j  a  v  a 2 s . c o  m*/

class Rectangle
{
    public int Width = 5;
    public int Height = 5;

}

class Program
{
    static void change(Rectangle r)
    {
        r = null;
    }

    static void Main(string[] args)
    {
        Rectangle r = new Rectangle();
        Console.WriteLine(r.Width);
        change(r);
        Console.WriteLine(r.Width);
    }
}

The output:

Even if we set the reference in change method to null, the r in the main method still points the rectangle object.

Next chapter...

What you will learn in the next chapter:

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