How to adjust the height of the window dynamically in WPF?

I have a model window that contains expander control.

This expander control when expanded shows the user control which allow user to enter input through textboxes.

When expande开发者_JS百科r control is collapsed it hides the user control.

I want when expander is collapsed or expanded the window will resize its height accordingly at run time.

Pleas help!!

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You can set property SizeToContent="WidthAndHeight", see also on SizeToContent on MSDN