Distinct and Reverse Operations Using LINQ

Introduction

Today, in this article let's play around with the most useful operations "Distinct" and "Reverse" in LINQ.

Distinct Operation using LINQ

Question: What is a "distinct" operation?

In simple terms "It provides filtering of data without any duplication of result sets.".

Step 1: The data in the database looks like this:

Step 2: Create a new "ASP.NET Web Application", as in:

Step 3: The complete code of WebForm1.aspx looks like this:

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

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

.grid

{

margin-top: 50px;

}

</style>

</head>

<body>

<div>

<table>

<tr>

<asp:Label ID="Label1" runat="server" Text="Distinct Operation using LINQ" Font-Bold="true"

Font-Size="Large" Font-Names="Verdana" ForeColor="Maroon"></asp:Label>

</td>

</tr>

<tr>

<asp:Button ID="Button1" runat="server" Text="Select Data" Font-Names="Verdana" Width="213px"

BackColor="Orange" Font-Bold="True" OnClick="Button1_Click" />

</td>

</tr>

<tr>

<asp:GridView ID="GridView1" runat="server" CssClass="grid" BackColor="LightGoldenrodYellow"

BorderColor="Tan" BorderWidth="1px" CellPadding="2" ForeColor="Black" GridLines="None">

</asp:GridView>

</td>

</tr>

</table>

</div>

</center>

</form>

</body>

</html>

Step 4: The complete code of WebForm1.aspx.cs looks like this:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

namespace DistinctLINQApp

{

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

{

protected void Page_Load(object sender, EventArgs e)

{

}

protected void Button1_Click(object sender, EventArgs e)

{

var query = (from r in objEntities.Employeeselect new

{

FirstName = r.FirstName, LastName = r.LastName, Age = r.Age

}

).Distinct();

GridView1.DataSource = query;GridView1.DataBind();

}

#region Instance MembersCompanyEntities objEntities = new CompanyEntities();

#endregion

}

Step 5: The output of the application looks like this:

Step 6: The data retrieved output of the application looks like this:

Reverse Operation in LINQ-to-XML

Question: What is a "reverse" operation using LINQ-to-XML?

In simple terms "It enables performing the result set to be printed in the reverse data format".

Step 1: Create a new "ASP.NET Web Application", as in:

Step 2: The complete code of Employee.xml looks like this:

<?xml version="1.0" encoding="utf-8" ?>

<FirstName>Vijay</FirstName>

<LastName>Prativadi</LastName>

</Employee>

<FirstName>Swetha</FirstName>

<LastName>Prativadi</LastName>

</Employee>

<LastName>Reddy</LastName>

</Employee>

</employees>

Step 3: The complete code WebForm1.aspx looks like this:

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

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

.grid

{

margin-top: 50px;

}

</style>

</head>

<body>

<div>

<table>

<tr>

<asp:Label ID="Label1" runat="server" Text="Reverse Operation using LINQ" Font-Bold="true"

Font-Size="Large" Font-Names="Verdana" ForeColor="Maroon"></asp:Label>

</td>

</tr>

<tr>

<asp:Button ID="Button1" runat="server" Text="Select Data" Font-Names="Verdana" Width="213px"

BackColor="Orange" Font-Bold="True" OnClick="Button1_Click" />

</td>

</tr>

<tr>

<asp:GridView ID="GridView1" runat="server" CssClass="grid" BackColor="LightGoldenrodYellow"

BorderColor="Tan" BorderWidth="1px" CellPadding="2" ForeColor="Black" GridLines="None">

</asp:GridView>

</td>

</tr>

</table>

</div>

</center>

</form>

</body>

</html>

Step 4: The complete code WebForm1.aspx.cs looks like this:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Xml.Linq;

namespace LINQReverseOperationApp

{

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

{

protected void Page_Load(object sender, EventArgs e)

{

}

protected void Button1_Click(object sender, EventArgs e)

{

XElement employee = XElement.Load(@"c:\users\administrator\documents\visual studio 2010\Projects\LINQReverseOperationApp\LINQReverseOperationApp\Employee.xml");

var query = (from r in employee.Descendants("FirstName") select new

{

FirstName = (string)r

}).Reverse();

GridView1.DataSource = query;

GridView1.DataBind();

}

Step 5: The output of application looks like this:

Step 6: The data retrieved output of application looks like this: