bool? is nullable while bool is not.
bool? first;
bool second;
In the above code, first will be null while second will be false .
The ? symbol after a type is only a shortcut to the Nullable type, bool? is equivalent to Nullable<bool> .
bool is a value type, this means that it cannot be null , so the Nullable type basically allows you to wrap value types, and being able to assign null to them.
bool? can contain three different values: true , false and null .
x y x & y x | y
true true true true
true false false true
true null null true
false true false true
false false false false
false null false null
null true null true
null false false null
null null null null
REF: https://stackoverflow.com/questions/1181491/whats-the-difference-between-bool-and-bool
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