how to differentiate between events of many controls added during runtime

Question

i am adding more than one link button during runtime but they all have the same name. so how can i differentiate between their events because i want everyone to have a different parameter or variable. this is my code:

while(drr.Read())
            {
                LinkButton lb = new LinkButton();
                lb.Click += new EventHandler(lb_Click);

                lb.Text = drr[2].ToString();

                PlaceHolderQuestions.Controls.Add(lb);

            }

and outside that there is the event handler:

void lb_Click(object sender, EventArgs e)
    {
        DownloadFile();
    }

how can i know which button is pressed?

Answer 1

You can use CommandArgument to differentiate the link buttons.

// Define Button : 
LinkButton lb = new LinkButton();
lb.CommandArgument = drr[2].ToString();
lb.Command += new CommandEventHandler(lb_Command);

void lb_Command(Object sender, CommandEventArgs e)
{
    string stringToDifferentiateButton = e.CommandArgument.ToString();
    DownloadFile();
}

Answer 2

You have the parameter Sender. It is the object pointer of the calling object, in your case one of the LinkButtons.

Test if sender is of type LinkButton. If so, read its text, and you know which it was.

Let's say, the buttons Text is the file to download:

void lb_Click(object sender, EventArgs e)
{
  if (Sender is LinkButton)
  {
    DownloadFile((Sender as LinkButton).Text);
  }
}

The line

if (Sender is LinkButton)

is necessary to prevent a runtime exception, if somebody decided to use lb_Click as an event on another component. ListBox would be a candidate, as it also abbreviates to lb (if the person respects polish notation in the first place).

You could enhance the function to work with other components easily:

void lb_Click(object sender, EventArgs e)
{
  if (Sender is LinkButton)
  {
    DownloadFile((Sender as LinkButton).Text);
  } else
  if (Sender is ListBox)
  {
    DownloadFile((string)(Sender as ListBox).SelectedItem);
  }
}

Answer 3

void lb_Click(object sender, EventArgs e)
{
    if (sender is LinkButton)
    {
       switch ((sender as LinkButton).Text)
       {
            case "Download":
                DownloadFile();
                break;
            case "Open":
                OpenFile();
                break;
            case "Log Out":
                LogOut();
                break;
        }
    }
}