Nullable types, works only with value types
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using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace NullableTypes { class Program { static void Main(string[] args) { int? i = dr.GetIntFromDataBase() ?? 100; // using of ?? like if/else int? i = dr.GetIntFromDataBase(); if (i.HasValue) { Console.WriteLine("ok,value={0}",i.Value); } else { Console.WriteLine("null"); } } } class DataBaseReader { int? nullableInt = 10; // also like Nullable<int> someNullableInt = 10; double? nullableDouble = 3.14; bool? nullableBool = null; // string? s = "oops"; // << only for value types //methods public int? GetIntFromDataBase() { return nullableInt; } public double? GetDoubleFromDataBase() { return nullableInt; } } } |