Why is IsChecked property nullable boolean in WPF CheckBox?

Question

Is there a case when IsChecked property on WPF CheckBox null ?

I guess that will answer my question from title of question.

Answer 1

If that is the case then it's probably a three-state-checkbox, have a look at http://msdn.microsoft.com/en-us/library/system.windows.forms.checkbox.threestate.aspx for an explaination.