How can I get all Labels on a form and set the Text property of those with a particular name pattern to string.empty?

Question

I want to clear all values on a form where the control is a label and its name starts with "label"

This code:

List<Label> lbls = this.Controls.OfType<Label>().ToList();
foreach (var lbl in lbls)
{
    if (lbl.Name.StartsWith("label"))
    {
        lbl.Text = string.Empty;
    }
}

...doesn't work, because the lambda is finding nothing - lbls.Count = 0.

Wouldn't this get ALL the controls on the form, even those that are children of other controls (such as, in my case, Panels)?

No, it does only find controls in the parent container. But i assume that you know what you want to find. So you just have to specify the container(s) you want to search. You can use `Concat` to add all labels. — Tim Schmelter, Oct 09 '12 at 21:51
I don't think this will search all the containers recursively — Sushanth --, Oct 09 '12 at 21:51
No, this.Controls contains only the first level of controls. Those directly hosted on the Form surface. — Steve, Oct 09 '12 at 21:53

score 8 · Accepted Answer · answered Oct 09 '12 at 21:58

8

Try to use this method:

public void ClearLabel(Control control)
{
   if (control is Label)
   {
       Label lbl = (Label)control;
       if (lbl.Text.StartsWith("label"))
           lbl.Text = String.Empty;

   }
   else
       foreach (Control child in control.Controls)
       {
           ClearLabel(child);
       }

}

You just need to pass form to ClearLabel method.

answered Oct 09 '12 at 21:58

Danilo Vulović

2,983
20
31

I had to change the lbl.Text.StartsWith() to lbl.Name.StartsWith(), but close enough. – B. Clay Shannon-B. Crow Raven Oct 09 '12 at 22:11

score 4 · Answer 2 · answered Oct 09 '12 at 21:54

No, it will not recursively search Panels.

To do what you want, you can do:

void changeLabel(Control c)
{
    if (lbl.Name.StartsWith("label"))
    {
        lbl.Text = string.Empty;
    }

    foreach(Control _c in c.Controls)
        changeLabel(_c);
}

score 1 · Answer 3 · answered Nov 19 '20 at 05:34

This does not touch the matter of recursion brought up in the previous answers; it's just another, a little more succint way of expressing what you had:

var labels = Controls.OfType<Label>().Where( x => x.Name.StartsWith("label") );
foreach (var label in labels)
{
    label.Text = "";
}

That's what I ended up writing, I thought of adding it here just for completeness - essentially, you don't need ToList(), and String.Empty hasn't had any advantage over "" for ages.

How can I get all Labels on a form and set the Text property of those with a particular name pattern to string.empty?

3 Answers3

Linked