The TabControl's height depends on the height of the selected TabItem. In order to achieve your requirement, you can get the height of the tab item's Content and assign it to the tab control's Height. You can subscribe for the SelectionChanged event of the TabControl and get the selected tab item, then call the Measure() method of the content and get the desired height. I have prepared a sample project where you can see how to implement the desired behavior.
Give this approach a try and let me know if you need any further assistance.
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