Removing all but one item from Controls

Question

I currently have a Sharepoint 2010 web part which includes several labels. I want to programmatically remove all but one of these labels.

I tried the code below but got a System.InvalidOperationException because obviously one can't modify a collection while iterating through it. However, I don't know how else to try this.

    private void clearLabels()
    {
        foreach (Control cont in this.Controls)
            if (cont is Label && cont.ID != "error")
                this.Controls.Remove(cont);
    }

score 5 · Accepted Answer · answered Jul 12 '11 at 13:03

5

Iterate over it backwards.

for(int i = this.Controls.Count - 1; i >= 0; i--)
{
    if (this.Controls[i] is Label && this.Controls[i].ID != "error")
    {
        this.Controls.Remove(this.Controls[i]);
    }
}

answered Jul 12 '11 at 13:03

canon

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score 1 · Answer 2 · answered Jul 12 '11 at 13:11

You are correct as to why you are getting the error. The following using Linq and ToArray() to solve the problem:

private void clearLabels()
    {
        foreach (from cont in this.Controls).ToArray()
            if (cont is Label && cont.ID != "error")
                this.Controls.Remove(cont);
    }

I would refactor this even further to:

private void clearLabels() {

    foreach (from cont in this.Controls 
             where cont is Label && cont.ID != "error"
            ).ToArray()
        this.Controls.Remove(cont);
}

Removing all but one item from Controls

2 Answers2

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