VS 2015 - Blend: Rotated Shape resizes wrong

Question

Hello,

 

 I'm trying to  learn and understand WPF and for this purpose I'm playing currently with Blend intergrated in the Community Edition of VS2015.

 

Create an empty WPF All.

Add a triangle shape to the main window.

Transform: rotate it by 90.

Until yet the resize works correct, i.e. when you change x and/or y the resizing is correct.

 

Now change it into a control (Select triangle, then the menu Tools-Make into Control).

 Select "Button" as target type.

Define it in "Application".

 Click OK.

 Now the new control exists of two parts: the triangle and a button. If you resize the button in the x/y axes the triangle resizes wrong.

Resizing the triangle itself is correct, BUT when creating another a user control, where this triangle button will be part of, the resizing of the button

results in the same wrong behaviour.

 

 Does anybody know where my problem is? Shall I rotate the button part, too? where is it defined?