Question

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What does the bool? return type mean?

I came a cross the following property in a class

public long? EmployeeId { get; set; }

I googled this operator with no luck, according to the MSDN MSDN OPERATOR there is only the operators ?? null-coalescing operator and ?: conditional operator.
but what about ?

Answer 1

In this case ? is not an operator. It is a shorter way to write: Nullable<long>

T? is exactly the same as Nullable<T> (with T a type)

It is called a nullable type (see MSDN)

It is used to allow “non-nullable” type (like int, long, a struct) to be assigned a null value.

It is useful when you need a possible invalid state for a value type, or if the data is being retrieved from a database that may contain a null value.