Make all Controls on a Form read-only at once

Question

Does anyone have a piece of code to make all Controls (or even all TextBoxes) in a Form which is read-only at once without having to set every Control to read-only individua

Answer 1

Write an extension method which gathers controls and child controls of specified type:

public static IEnumerable GetChildControls(this Control control) where T : Control
{
    var children = control.Controls.OfType();
    return children.SelectMany(c => GetChildControls(c)).Concat(children);
}

Gather TextBoxes on the form (use TextBoxBase to affect RichTextBox, etc - @Timwi's solution):

IEnumerable textBoxes = this.GetChildControls();

Iterate thru collection and set read-only:

private void AreTextBoxesReadOnly(IEnumerable textBoxes, bool value)
{
    foreach (TextBoxBase tb in textBoxes) tb.ReadOnly = value;
}

If want - use caching - @igor's solution