Private int? _City_Id; can anyone tell me that "?" mean here

Question

private int? _City_Id;

Answer 1

Without knowing your target language for an answer, using C # 2.0 ? denotes types of valid values.

Invalid value types (indicated by a question mark, for example, int? I = null;) that add null to the set of valid values ​​for any value type.

Which, as Kalum points out (all of his loans), means that a variable can be assigned null. Typically, primitives of type intand doublecannot be null,

int? x = 10;
double? d = 4.108