Gets or sets whether the toggle switch editor supports three states (checked, unchecked and indeterminate).
true if the editor supports three states; false if the editor supports two states (checked and unchecked).
A toggle switch editor supports three states (checked, unchecked and indeterminate) if its IsThreeState property is set to true. Otherwise, if this property is set to false, only checked and unchecked states are supported.
After the ToggleSwitchEdit.IsChecked property's value has been changed, the check editor fires the corresponding event (ToggleSwitchEdit.Checked, ToggleSwitchEdit.Unchecked or ToggleSwitchEdit.Indeterminate).