"Expander" in Windows Forms

I have the following situation.

Need:

• A - always visible;
• B - "hiddable";
• Form1 - resizable; 开发者_如何学Python
• The most right visible panel Docked.
• In the case in the picture, B should collapse, minimizing the form to the "A" size...

Apparently it is simple, but I tried some hours and posted this topic.

---

I used as base a Form + SplitContainer with a docked-to-right button in the Panel1. There is a need to remember the actual Form size and to reestablish it when the button expands, or to reduce the form size to the Panel1 size when the form "collapses".

---

You can use TableLayoutPanel with AutoSize for B column. When user click Expand you show show content of B and Resize Form Width via code.