Assign vs create new delegate

Question

In sample in MSDN regarding Invoke I found strange expression for my while setting delegate variable:

Why they use syntax of creating new object:

myDelegate = new AddListItem(AddListItemMethod);

instead of assigment

myDelegate = AddListItemMethod;

What is the difference between these expressions? What is the meaning of expression new AddListItem(...) ?

Whole code:

 public class MyFormControl : Form
   {
      public delegate void AddListItem();
      public AddListItem myDelegate;
      private Button myButton;
      private Thread myThread;
      private ListBox myListBox;
      public MyFormControl()
      {
         myButton = new Button();
         myListBox = new ListBox();
         myButton.Location = new Point(72, 160);
         myButton.Size = new Size(152, 32);
         myButton.TabIndex = 1;
         myButton.Text = "Add items in list box";
         myButton.Click += new EventHandler(Button_Click);
         myListBox.Location = new Point(48, 32);
         myListBox.Name = "myListBox";
         myListBox.Size = new Size(200, 95);
         myListBox.TabIndex = 2;
         ClientSize = new Size(292, 273);
         Controls.AddRange(new Control[] {myListBox,myButton});
         Text = " 'Control_Invoke' example";
         myDelegate = new AddListItem(AddListItemMethod);
      }
      static void Main()
      {
         MyFormControl myForm = new MyFormControl();
         myForm.ShowDialog();
      }
      public void AddListItemMethod()
      {
         String myItem;
         for(int i=1;i<6;i++)
         {
            myItem = "MyListItem" + i.ToString();
            myListBox.Items.Add(myItem);
            myListBox.Update();
            Thread.Sleep(300);
         }
      }
      private void Button_Click(object sender, EventArgs e)
      {
         myThread = new Thread(new ThreadStart(ThreadFunction));
         myThread.Start();
      }
      private void ThreadFunction()
      {
         MyThreadClass myThreadClassObject  = new MyThreadClass(this);
         myThreadClassObject.Run();
      }
   }

// The following code assumes a 'ListBox' and a 'Button' control are added to a form, 
// containing a delegate which encapsulates a method that adds items to the listbox.

   public class MyThreadClass
   {
      MyFormControl myFormControl1;
      public MyThreadClass(MyFormControl myForm)
      {
         myFormControl1 = myForm;
      }

      public void Run()
      {
         // Execute the specified delegate on the thread that owns
         // 'myFormControl1' control's underlying window handle.
         myFormControl1.Invoke(myFormControl1.myDelegate);
      }
   }

Nothing, see [here](https://sharplab.io/#v2:EYLgtghgzgLgpgJwDQxASwDYB8ACAGAAhwEYBuAWACgcBmIgJgIGECBvKgzounAFgICyACgCUbDl0klGEAMbECAXkEVKkqcRmzGygHZwA7kU1CBI1eq4TLJAJxC5CgIR6Arhgznr6uw+0EXAl13TwsuAF8qcKA==) (right pane, IL code) The second one is converted to the first one. — xanatos, Jun 12 '18 at 08:19

score 5 · Accepted Answer · answered Jun 12 '18 at 08:19

5

There is no difference.

The new syntax is what was required long time ago and since then they made c# compiler smart enough to create this code for you when you assign method to delegate variable.

answered Jun 12 '18 at 08:19

Rafal

12,391
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Assign vs create new delegate

1 Answers1