Question

For my current project I am adding an variable amount of usercontrols : ucTask to my flowlayoutpanel : flpTasks

foreach (task t in tasks)
{
   ucTask uct = new ucTask();
   uct.id = t.task_id;
   uct.date= t.date.ToString();
   uct.btnNaam = t.task_id.ToString();

   uct.OnButtonclick += new EventHandler(uct_OnButtonclick);

   flpTasks.Controls.Add(uct);
}

Now I will have a couple of those usercontrols in the flowlayoutpanel, and I want to fire an event when I press that button. With the EventHandler I can fire an event, but I need to fire a different event for a different button.

    void uco_OnButtonclick(object sender, EventArgs e)
    {
        lblStatus.Text = "TEST";
    }

I don’t know how to know which button (or usercontrol) I pressed. And I’m out of ideas, any suggestions?

Thanks,
Thomas

Answer 1

Sender of event is actually one of buttons. When you cast sender to Button type, you can access any of Buttons properties and determine which button was pressed:

void uco_OnButtonclick(object sender, EventArgs e)
{
   Button button = sender as Button;
   if (button == null)
       return;

   lblStatus.Text = button.Name;
}

UPDATE: after reading your question once again, I get that ucTask is actually UserControl, which rises event when button inside it was clicked.

So, first is naming. Good style for class names in c# is PascalCase. E.g. for task user control good name will be TaskControl. Next goes event naming. It’s common to name events as EventName(-ing, -ed). If you want to raise event, then good style is protected method OnEventName(-int, -ed). And another remark – when you writing user controls, you are free to use business terms to name your events. E.g. TaskCreated, TaskChanged. And you also can pass any parameters to your event by creating custom EventArgs.

So, for your user control:

public class TaskChangedEventArgs : EventArgs
{
    public TaskChangedEventArgs(int taskId)
    {
        TaskId = taskId;
    }
    public int TaskId { get; private set; }
}

public class TaskControl : UserControl
{
   public event EventHandler<TaskChangedEventArgs> TaskChanged;

   // raise it inside button click event handler
   protected void OnTaskChanged(int taskId)
   {
       if (TaskChanged != null)
           TaskChanged(this, new TaskChangedEventArgs(taskId));
   }
}

When you use your user control, just subscribe to its TaskChanged event:

uct.TaskChanged += new EventHandler<TaskChangedEventArgs>(uct_TaskChanged);

And all parameters, that you passed via event argument will be available in that event handler:

void uco_TaskChanged(object sender, TaskChangedEventArgs e)
{
    lblStatus.Text = e.TaskId.ToString();
}