CODEWITHSUNDEEP
c#events
Rob
Rob

Reputation: 109

Passing a Variable to an Event in .NET

For example I have a list of picture boxes that raise an event once the cursor hover over them. Yet I need somehow not only to rise this event, but also to pass the "i" variable, so that I would know which picturebox has the cursor over it.

for (int i = 0; i < 25; i++)
{
....
pbList.Add(new PictureBox());

pbList[i].MouseHover += new System.EventHandler(this.beeHideInfo);
                                            //// need to pass "i" here
}

and 

    private void beeShowInfo(object sender, EventArgs e)
    {
        lb_beeInfo.Text = "You are hovering over: "+beeList[i].name;
                                               /// need to get this "i"
    }

Any ideas?

Upvotes: 1

Views: 4051

Answers (6)

Rosmarine Popcorn
Rosmarine Popcorn

Reputation: 10967

another way might be if you create a Custom Picture Box

class CustomPictureBox : PictureBox
{
  public int id;
  public CustomPictureBox(int ID)
 {
   id = ID;
 }

}

firt place a GLOBAL id to parent and each time if a CustomPicureBox is clicked get the ID than everywhere you want to make changes to Clicked CustomPicutreBox test it

foreach(CustomPicutreBox i in Control.controls)
{
  if(i.ID == sender.ID)
  doWhatEveryYouWant(); 
}
}

Upvotes: 1

JaredPar
JaredPar

Reputation: 754565

The easiest way to do this is use an anonymous function to explicitly pass the PictureBox or index instance into the handler.

for (int i = 0; i < 25; i++)
{
  ....
  var box = new PictureBox();
  pbList.Add(box);
  box.MouseHover += delegate { this.beeShowInfo(box); }
}

private void beeShowInfo(PictureBox box) 
{
   lb_beeInfo.Text = "You are hovering over: "+box.Name;
}

Upvotes: 1

Gabe
Gabe

Reputation: 86708

The object sender parameter is the PictureBox sending the event. If you need to associate something with that object, you can use its Tag member:

for (int i = 0; i < 25; i++)
{
    ....
    pbList.Add(new PictureBox() { Tag = beeList[i] });
    pbList[i].MouseHover += new System.EventHandler(this.beeHideInfo);
}

and 

private void beeShowInfo(object sender, EventArgs e)
{
    PictureBox pb = (PictureBox)sender;
    Bee b = (Bee)pb.Tag;
    lb_beeInfo.Text = "You are hovering over: "+b.name;
}

Upvotes: 3

Uwe Keim
Uwe Keim

Reputation: 40726

You could you do something like:

for (int i = 0; i < 25; i++)
{
    ...

    pbList.Add(new PictureBox());

    var index = i;
    pbList[i].MouseHover += 
        delegate
        {
            lb_beeInfo.Text = "You are hovering over: "+beeList[index].name;
        };
}

I.e. use an anonymous method.

As John Saunders says, there is an easier solution.

Upvotes: 1

Robert Levy
Robert Levy

Reputation: 29073

Assuming pbList and beelist contain related items in the same order, you can do something like beeList[ pbList.IndexOf(sender) ].name

Upvotes: 2

John Saunders
John Saunders

Reputation: 161773

You cannot pass variables to an event.

Besides, the necessary variable has already been passed to you: sender.

sender is a reference to the object which raised the event. In your case, it's a reference to the PictureBox that raised the event.

Upvotes: 5

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