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Context Menus 101

Posted on 2004-10-06
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Last Modified: 2010-04-15
I have added a Context Menu (popup) to a Windows Form.

At runtime....when I right-click on the associated control....the popup menu activates and shows "Add"

But when I click on Add...nothing happens because I have not associated an event handler for the click on Add.

How do I do this?
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Question by:Tom Knowlton
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8 Comments
 
LVL 15

Accepted Solution

by:
Timbo87 earned 500 total points
ID: 12241969
If you're using Visual Studio .NET, just double-click the Add menu option in design mode. Otherwise here is an example with a delegate.

Declaring the Add button:
private MenuItem menuItem;

Hooking up an event handler with a delegate:
menuItem.Click += new EventHandler(menuItem_Click);

The event handler:
private void menuItem_Click(object sender, EventArgs e)
{
     MessageBox.Show("Add");
}

0
 
LVL 5

Author Comment

by:Tom Knowlton
ID: 12242000
I am actually adding the pop-up menu items at runtim using the ContextMenu popup event:

private void contextMenuTreeMod_Popup(object sender, System.EventArgs e)
            {
                  // Define the MenuItem objects to display for the TextBox.
                  MenuItem menuItem1 = new MenuItem("&Add");                  
                  
                  // Clear all previously added MenuItems.
                  contextMenuTreeMod.MenuItems.Clear();
 
                  if(contextMenuTreeMod.SourceControl == treeViewInventory)
                  {
                        // Add MenuItems to display for the TextBox.
                        contextMenuTreeMod.MenuItems.Add(menuItem1);                        
                  }
            }      





My intent is for THIS method to fire when the user clicks on ADD..........but the method is not WIRED to the CLICK EVENT

            protected void menuItem1_Click(System.Object sender, System.EventArgs e)
            {
                  // Insert code to handle Click event.
                  MessageBox.Show("Add something to");
            }
0
 
LVL 5

Author Comment

by:Tom Knowlton
ID: 12242036
Ohhhhhh...........I get it.....duh...............


This works:


            private void contextMenuTreeMod_Popup(object sender, System.EventArgs e)
            {
                  // Define the MenuItem objects to display for the TextBox.
                  MenuItem menuItem1 = new MenuItem("&Add");                  

                  menuItem1.Click += new EventHandler(menuItem1_Click);    ////////////////////////////////////  JUST NEEDED TO ADD THIS PART......AS YOU SUGGESTED.....////////////////////////
                  
                  // Clear all previously added MenuItems.
                  contextMenuTreeMod.MenuItems.Clear();
 
                  if(contextMenuTreeMod.SourceControl == treeViewInventory)
                  {
                        // Add MenuItems to display for the TextBox.
                        contextMenuTreeMod.MenuItems.Add(menuItem1);                        
                  }
            }      

            protected void menuItem1_Click(System.Object sender, System.EventArgs e)
            {
                  // Insert code to handle Click event.
                  MessageBox.Show("Add something to");
            }
            


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LVL 5

Author Comment

by:Tom Knowlton
ID: 12242074
Let me ask you this:


How would I   UNWIRE     the ADD click event from one method............. and then REWIRE the ADD click event to some other method:


My best guess:

  private void contextMenuTreeMod_Popup(object sender, System.EventArgs e)
          {
               // Define the MenuItem objects to display for the TextBox.
               MenuItem menuItem1 = new MenuItem("&Add");              

               menuItem1.Click += new EventHandler(menuItem1_Click);    ////////////////////////////////////  JUST NEEDED TO ADD THIS PART......AS YOU SUGGESTED.....////////////////////////


           


             //CAN I USE     -=      to     unassign the event handler?????????????????





               
               // Clear all previously added MenuItems.
               contextMenuTreeMod.MenuItems.Clear();
 
               if(contextMenuTreeMod.SourceControl == treeViewInventory)
               {
                    // Add MenuItems to display for the TextBox.
                    contextMenuTreeMod.MenuItems.Add(menuItem1);                    
               }
          }    

          protected void menuItem1_Click(System.Object sender, System.EventArgs e)
          {
               // Insert code to handle Click event.
               MessageBox.Show("Add something to");
          }
         
          protected void menuItem1Alt_Click(System.Object sender, System.EventArgs e)
          {
               // Insert code to handle Click event.
               MessageBox.Show("ALTERNATE Add something to");
          }
         
0
 
LVL 15

Expert Comment

by:Timbo87
ID: 12242258
Yes, you can use -= to remove delegates. You can also wire up multiple event handlers if you need to.
0
 
LVL 5

Author Comment

by:Tom Knowlton
ID: 12242297
wire-up multiple event handlers?

you mean several differnt event handlers for one click....and the one that gets used depends on something?

can you explain?
0
 
LVL 15

Expert Comment

by:Timbo87
ID: 12242391
Multicasting is the ability to call multiple methods with a single delegate.

EventHandler a = new EventHandler(method1);
EventHandler b = new EventHandler(method2);
EventHandler c = new EventHandler(method3);

menuItem.Click = a + b + c;

Then you can add or remove them with += or -=.
0
 
LVL 5

Author Comment

by:Tom Knowlton
ID: 12242800
Interesting.
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