Why is the IsChecked
property of a checkbox control in WPF of type bool?
(or Nullable<bool>
). I mean how can a checkbox control have the value of null
?
Yes the null value exists and appears as a filled box. It indicates "Not Applicable" to the system.
According to the documentation , the IsChecked
property has three different possible states:
So, when IsChecked
is set to null
, the check box will show an "indeterminate" state. This is commonly represented as a shaded, or greyed-out, control.
复选框可以具有第三个灰色的不确定状态。
不要忘记将复选框的属性IsThreeState设置为true以启用此功能。
Because WPF supports binding. If we bind a DB boolean column value to a checkbox. That column may have True/False/Null values. That means it has three values for a boolean field. So the WPF UI also should handle the three state.
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