How to remove border between window title and content

Question

I created a window with ribbons (2010 - Microsoft.Windows.Controls.Ribbon ).

It looks like this:

Now, is there a border above the tabs (between the tabs and the title). This is very ugly.

It should look like Microsoft Office Word:

What can I do so that there is no border between the tabs and the title?

(used by RibbonWindow)

Answer 1

Now I use Fluent Ribbon , which solve the problem.

Answer 2

It looks like you are using a standard WPF window. Instead, try using the RibbonWindow frame. It integrates the ribbon into the window itself, and not just contains it as a regular control, which is what the Window does.