How can I set a checkbox to default as Intermediate?

Given the following declaration of a CheckBox in XAML created in Visual Studio Community 2015 in C#, how can I define the state of the CheckBox to be Intermediate on creation?

<CheckBox Margin="95,121,0,807" IsThreeState="True" IsChecked="True">Binary</CheckBox>

I have already sifted through the MSDN API for a few hours scanning these pages: http://ift.tt/1JrxA6x http://ift.tt/1YubrRc

I cannot seem to find a way to do this. Is it possible to initialize a CheckBox to the intermediate state?