Effective Paging Using LINQ (Sample Code)

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Introduction

Binding gridview with paging using LINQ is a nice way to bind large amount of data with efficient speed. Two LINQ operators Skip and Take make this task very easy.

Background 

HOW DO WE ACHIEVE EFFECTIVE PAGING FROM LINQ ON SERVER SIDE ? 

If you are familiar with LINQ and its techniques, then you must read about Deferred Execution of LINQ. Deferred Execution in LINQ depicts that LINQ executes query when it is about to use, means when we are using var of LINQ, not when we write it. You can learn more about deferred execution here. 

Using the Code

Skip and Take operators allow you to only pull back the records you need. 

If you are not interested in reading this article, you can simply download the code from the link at the top of this article. There, you will get the sample code of this article.

We can achieve effective paging by the following methods:

1. Stored procedure
2. From LINQ 

In the simple example below, I am using a LinqDataSource and handling its onselecting method to create our LINQ query and achieving effective paging. Set AutoPage to false because I am writing code to handle paging ourselves. Also the PageSize property of the GridView control is being populated from a integer constant in the code-behind class. 

On Aspx Page

<asp:gridview allowpaging="True" autogeneratecolumns="False" 
datasourceid="LinqDataSource1" id="GridView1" pagesize="<%# PAGE_SIZE %>" 
runat="server" width="276px">
        <columns>
            <asp:boundfield datafield="ProductID" headertext="PID" readonly="True" 
		sortexpression="ProductID">
            <asp:boundfield datafield="ProductName" headertext="ProductName" 
		readonly="True" sortexpression="ProductName">
            <asp:boundfield datafield="UnitPrice" headertext="UnitPrice" 
		readonly="True" sortexpression="UnitPrice">
            
        </asp:boundfield></asp:boundfield></asp:boundfield></columns>
        </asp:gridview>
        

        <asp:linqdatasource autopage="False" contexttypename="DataClassesDataContext" 
		entitytypename="" id="LinqDataSource1" onselecting="LinqDataSource1_Selecting" 
	runat="server" select="new (ProductID, ProductName, UnitPrice)" tablename="Products">
        </asp:linqdatasource>   

On Code Behind   

DataClassesDataContext db = new DataClassesDataContext();
protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
    }
}
public const int PAGE_SIZE = 10;

protected void LinqDataSource1_Selecting(object sender, LinqDataSourceSelectEventArgs e)
{
    // LINQ query


    var query = from m in db.Products
                select m;

    // Set the total count
    // so GridView knows how many pages to create
    e.Arguments.TotalRowCount = query.Count();

    // Get only the rows we need for the page requested
    query = query.Skip(GridView1.PageIndex * PAGE_SIZE).Take(PAGE_SIZE);

    e.Result = query;
}

Download the sample code for LINQ effective paging and paging from the stored procedure.

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