C# bool? 的意思

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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    truetrue    false   false   truetrue    null    null    truefalse   true    false   truefalse   false   false   falsefalse   null    false   nullnull    true    null    truenull    false   false   nullnull    null    null    null


REF: https://stackoverflow.com/questions/1181491/whats-the-difference-between-bool-and-bool

C# bool? 的意思