How to handle dynamic GUIs in .net

Question

Hi All,

I've come accross a problem, that is probably seen pretty often, but has never really been discussed here.

In my Gui, I'm adding Controls in a for loop to a Flowpanellayout. The point is to display "reports" from a database. It has to be dynamic, because the number of reports can be different from day to day.

---

Pseudocode Adding Gui Elements:

for(int i = 0; i < reports.Count; i++)
{
    TextBox textboxPerson = new TextBox();
    textboxPerson.Name = "TextboxName" + i;
    textboxPerson.Text = reports[i].Name;
    textboxPerson.TextChanged += new EventHandler(this.textboxPerson_TxtChanged);

    Label labelToChange = new Label();
    labelToChange.Name = "label"+i;
    labelToChange.Text = "";

    flowlayoutPanel.Controls.Add(textboxPerson);
    flowlayoutPanel.Controls.Add(labelToChange);
}

Event Handler:

private void textboxPerson_TextChanged(object sender, EventArgs e)
{
   //So far, I'm only getting the number of the Textbox that changed.
}

---

Here is, where I need your advise. The Textboxs and Labels are matching (iE, Texbox1 is as you can see connected to Label1). But how do I adress one Control in particular?

• If Texbox1's Text changes, how do I address Label1 to change its Text or something?
• Is there a state of the art of adding dynamic Gui Elements to a Form and handling them?

Thank you for your answers

Answer 1

You can use the Tag property of the controls, for instance. In your loop, you can assign the Label to the Tag property of the TextBox like this:

TextBox textboxPerson = new TextBox();
// do the stuff with the text box

Label labelToChange = new Label();
// do the stuff with the label
textboxPerson.Tag = labelToChange

Then you can get to the Label in the TextChanged event of the TextBox:

private void textboxPerson_TextChanged(object sender, EventArgs e)
{
   //So far, I'm only getting the number of the Textbox that changed.
   Label theLabel = (sender as TextBox).Tag;
   theLabel.Text = "whatever should go here";
}

Answer 2

You could think of writing your own little UserControl, which groups the TextBox and the Label. This is especially useful if your generated control set becomes larger (e.g. you are adding a button or two).

Best Regards

Answer 3

In your particular case, you can use data binding to link the Label to the TextBox:

for (int i = 0; i < reports.Count; i++) {
  TextBox textboxPerson = new TextBox();
  textboxPerson.Name = "TextboxName" + i;
  textboxPerson.Text = reports[i].Name;
  //textboxPerson.TextChanged += new EventHandler(this.textboxPerson_TxtChanged);

  Label labelToChange = new Label();
  labelToChange.Name = "label" + i;
  labelToChange.Text = "";

  // this will update labelToChange.Text whenever textboxPerson.Text changes
  labelToChange.DataBindings.Add("Text", textboxPerson, "Text");

  flowlayoutPanel.Controls.Add(textboxPerson);
  flowlayoutPanel.Controls.Add(labelToChange);
}

If you use this, you don't even have to handle the TextChanged event

Answer 4

Do like this in your event handler:

string labelName = ((Control)sender).Name.Replace("TextboxName","label");
Label [] labels = FlowlayoutPanel.Controls.Find(labelName,false);
if (labels.Length > 0)
    labels[0].Text = "This is your attached label";