‫مقایسه value type و reference type

struct Point
{
   private int x, y;             // private fields
 
   public Point (int x, int y)   // constructor
   {
         this.x = x;
         this.y = y;
   }

   public int X                  // property
   {
         get {return x;}
         set {x = value;}
   }

   public int Y
   {
         get {return y;}
         set {y = value;}
   }
}

Point p1 = new Point();         // Point is a *struct*
Form f1 = new Form();           // Form is a *class*

Form f1;                        // Allocate the reference
f1 = new Form();                // Allocate the object

Point p2 = p1;
Form f2 = f1;

Point myPoint = new Point (0, 0);      // a new value-type variable
Form myForm = new Form();              // a new reference-type variable
Test (myPoint, myForm);                // Test is a method defined below
 
void Test (Point p, Form f)
{
      p.X = 100;                       // No effect on MyPoint since p is a copy
      f.Text = "Hello, World!";        // This will change myForm’s caption since
                                       // myForm and f point to the same object
      f = null;                        // No effect on myForm
}

Point myPoint = new Point (0, 0);      // a new value-type variable
Form myForm = new Form();              // a new reference-type variable
Test (ref myPoint, ref myForm);        // pass myPoint and myForm by reference
 
void Test (ref Point p, ref Form f)
{
      p.X = 100;                       // This will change myPoint’s position
      f.Text = “Hello, World!”;        // This will change MyForm’s caption
      f = null;                        // This will nuke the myForm variable!
}

• قسمت reference متغیرهای محلی و پارامترهای از نوع reference-typed (مانند myTextBox)
• متغیرهای محلی و پارامترهای متد از نوع value-typed (مانند integer, bool, char, DateTime و ...)

using (Stream s = File.Create ("myfile.txt"))

{
   ...
}

Stream s = File.Create ("myfile.txt");

try
{
   ...
}

finally
{
   if (s != null) s.Dispose();
}

Size s = new Size (100, 100);          // struct = value type
Font f = new Font (“Arial”,10);        // class = reference type

Form myForm = new Form();

myForm.Size = s;
myForm.Font = f;

class Form
{
      // Private field members
      Size size;
      Font font;

      // Public property definitions
      public Size Size
      {
            get    { return size; }
            set    { size = value; fire resizing events }
      }

      public Font Font
      {
            get    { return font;  }
            set    { font = value; }
      }
}

myForm.ClientSize.Height = myForm.ClientSize.Height * 2;

Cannot modify the return value of 'System.Windows.Forms.Form.ClientSize' because it is not a variable

myForm.ClientSize = new Size (myForm.ClientSize.Width, myForm.ClientSize.Height * 2);