[CheckBox] Setting Checked = true doesn't work for Indeteminate state

[jmairboeck]

I'm not sure if this is a bug or not.

If a CheckBox's CheckState is Indeterminate, setting Checked = true (programmatically) doesn't work because the setter checks whether the new value differs from what the Checked getter returns (which is true for Indeterminate).

I expected that setting Checked = true would always be equivalent to setting CheckState = CheckState.Checked, so to actually change the state if it was Indeterminate before, even if the Checked getter already returns true before.