Null Coalescing Operator

Introduction

This article demonstrates one of interesting and most useful concept in C#.

Question: What is Null Coalescing Operator?

In simple terms "This operator is used to handle a variable when value is null, instead by perform an expected operation when value is null. The left side operand will be executed when value is not null else in null case will return right operand".

Step 1: Create a new web application

Step 2: The complete code of WebForm1.aspx looks as below

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="NullCoalescingOperatorApp.WebForm1" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

</head>

<body>

<div>

Null Coalescing Operator App</h1>

<table>

<tr>

<asp:Button ID="Button1" runat="server" Text="Addition" Width="165px" Font-Names="Verdana"

BackColor="Orange" OnClick="Button1_Click" />

</td>

</tr>

</table>

<table>

<tr>

<asp:Label ID="lblResult" runat="server" Font-Names="Verdana" ForeColor="Brown"></asp:Label>

</td>

</tr>

</table>

</center>

</div>

</form>

</body>

</html>

Step 3: The complete code of WebForm1.aspx.cs looks as below

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

namespace NullCoalescingOperatorApp

{

public partial class WebForm1 : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

}

protected void Button1_Click(object sender, EventArgs e)

{

//When Value is NULL

//int? a = null;

//int b = a ?? 0;

//lblResult.Text = string.Format("Result is: {0}", b.ToString());

//When Value is NOT NULLint? a = 10;int b = a ?? 0;lblResult.Text = string.Format("Result is: {0}", b.ToString());

}

}

Step 4: The output for the application when value is null:

Step 5: The output for the application when value is not null