c# - cannot implicitly convert type 'bool?' to 'bool'. An explicit conversion exists (are you missing a cast?)

Question

Error : cannot implicitly convert type 'bool?' to 'bool'. An explicit conversion exists (are you missing a cast?)

Code :

Test obj = new Test();
obj.IsDisplay = chkDisplay.IsChecked;

but when I use this method to cast the property into a bool then there is no error.

Test obj = new Test();
obj.IsDisplay = (bool) chkDisplay.IsChecked;

I would like to know why I need to cast this bool to bool?

Answer 1

As the others stated bool? is not equal to bool. bool? can also be null, see Nullable<t> (msdn).

If you know what the null state wants to imply, you easily can use the ?? - null-coalescing operator (msdn) to convert your bool? to bool without any side effects (Exception).

Example:

//Let′s say "chkDisplay.IsChecked = null" has the same meaning as "chkDisplay.IsChecked = false" for you
//Let "check" be the value of "chkDisplay.IsChecked", unless "chkDisplay.IsChecked" is null, in which case "check = false"

bool check = chkDisplay.IsChecked ?? false;