Cause an exception "ReadOnly controls collection" - when editing UI

Question

I've taken over someone else's project and they have used Krypton Toolkit. When I change anything on the UI, (i.e., Add button, edit Text, add menu item), I get this exception error:

this.kryptonHeaderGroupMain.Controls.Add(this.kryptonHeaderGroupMain.Panel);

Cause an exception "ReadOnly controls collection"

..and it mucks up the Designer View.

What am I missing?

As some people recommended, I have tried it but still failed:

this.<kryptonControlsContainer>.Panel.Controls.Add(this.<otherControlName>);

Answer 1

The Controls property of the KryptonHeaderGroup control is a custom Controls Collection (it's named KryptonReadOnlyControls) which doesn't allow adding or removing child controls. The way KryptonHeaderGroup was designed is that it has a Panel which acts as the container for its child controls. What you need to do is as follows.

In design-mode:

Before adding any controls, make sure you select the panel and not the KryptonHeaderGroup itself. See the difference in these screenshots:

Using code:

//kryptonHeaderGroup1.Controls.Add(new KryptonButton());        // Throws an exception.
kryptonHeaderGroup1.Panel.Controls.Add(new KryptonButton());    // Works fine.

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Note: The same logic applies for other controls like KryptonGroupBox, KryptonGroup, and KryptonSplitContainer.