// You do this in the screenshot.

foreach (Control x in this.Controls)

{

    ...

    if (x.Location.Y > 1100)

    {

        this.Controls.Remove(x);

    }

    ...

    // Another foreach...

}

​

// You could do this instead..

var controlsToRemove = new List<Control>();

​

foreach (Control x in this.Controls)

{

    ...

    if (x.Location.Y > 1100)

    {

        if (!controlsToRemove.Contains(x))

        {

            controlsToRemove.Add(x);

        }

    }

    ...

    // Another foreach...

}

​

foreach (Control x in controlsToRemove)

{

    this.Controls.Remove(x);

}