C# : Implicit conversion between '<null>' and 'bool'

Question

I got a weird error message when I tried to convert an object to bool, here is my code:

public partial class ModifierAuteur : DevExpress.XtraEditors.XtraForm
{
    public ModifierAuteur(object getKeyDecesCheckBox)
    {
         decesCheckBox.Checked = getKeyDecesCheckBox == null ? null : (bool)getKeyDecesCheckBox;
    }
}

and this is the error message :

Type of conditional expression cannot be determined because there is no implicit conversion between <null> and bool

Answer 1

Assuming that the assignment is possible, you need to convert to a nullable bool, like this:

decesCheckBox.Checked = getKeyDecesCheckBox == null ? null : (bool?)((bool)getKeyDecesCheckBox);

The inner cast to bool unboxes the value, and the outer cast to bool? makes it compatible with null of the conditional expression.

If the left-hand side of the assignment does not allow nulls, you need to decide on the value to set when getKeyDecesCheckBox is null. Usually, that's a false:

 decesCheckBox.Checked = getKeyDecesCheckBox == null ? false : (bool)getKeyDecesCheckBox;