Question

I have a wpf TreeView with customized Items.
Each node is a wpf Border with a wpf expander inside. The expander contains the child items of the node, and so on. So every TreeViewNode has its items inside.

TreeViewItem: UI Representation:

the outer element: a wpf Border (the node): 

/-----------------\
|                 |
| title(textbox)  |
|                 |
|  \/Expander     |
|  |        |     |
|  | child  |     |
|  | items  |     |
|  ----------     |
|                 |
\-----------------/

The Viewmodel for the TreeViewItem has an ObservableCollection of further TreeviewItems.

If I add items using ObservableCollection<Item>.Add(..),
the TreeviewItem View shows the node with the new item: it enlarges the wpf Border and shows the new item inside the wpf Expander.

If I remove Items using ObservableCollectionyItem>.Remove(..), The Border shrinks again and shows an empty expander.

This is the behavior that I want to keep!

Problem: I used for the TextBox:

DockPanel.Dock = "Top" 

to fit to the Border width. This stretches the TextBox to fit the new border width.
When I remove a child Item, the border won’t get reduced in width, because the TextBox
is now larger. But I want the TextBoxto be independant from the outer border.

The TextBox should resize to the available space, when child items are added,
but should not influence the border from snapping back to a smaller size, when child items are removed.There should be no dependency from the TextBox width to any Layout elements.
How to achieve this?

example: If I use DockPanel.Dock="Left" for the textbox,
it will not grow (not good), but the border will snap back to its former size (good), when removing elements.

How can I make the width of the textbox not be relevant for the wpf automatic UI sizing ? By the way, I don’t want to size the treeviewitems from code.

Answer 1

I found a very useful hint here:

stackoverflow.com/questions/6338315/allow-wpf-grid-cell-content-to-expand-outside-of-the-grid-cell

If you put the textbox inside a canvas, it won’t influence the outer border width!