Nullable Types - CSharp Language Basics

CSharp examples for Language Basics:Nullable

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Introduction

Reference types can represent a nonexistent value with a null reference.

Value types, however, cannot ordinarily represent null values. For example: 

string s = null;       // OK, Reference Type
int i = null;          // Compile Error, Value Type cannot be null

To represent null in a value type, you must use a special construct called a nullable type.

A nullable type is denoted with a value type followed by the ? symbol: 

int? i = null;                     // OK, Nullable Type
Console.WriteLine (i == null);     // True

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