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previous DevX article, you saw the basic process for using the LinqDataSource control to retrieve and display data. That article discussed functionality such as passing parameters to a LINQ query and executing a stored procedure. This article builds on that foundation by discussing more sophisticated features for creating fully-editable pages, such as adding Create, Read, Update, and Delete (CRUD) capabilities, and handling CRUD events generated by the LinqDataSource control. In addition, this installment also demonstrates how to aggregate and group data using the LinqDataSource control.
CRUD with LinqDataSource
To begin, create a new Visual C# web site named
LinqDataSourceExample. After creating the web site, select Website → Add New Item from the menu. In the Add New Item dialog box, select the "LINQ to SQL Classes" template, and name it
AdventureWorksDatabase.dbml. You'll see the Object Relational Designer view of the newly created class. From that view, select View → Server Explorer from the menu, and add a new data connection to the AdventureWorks database. Finally, to create the corresponding entity classes, drag and drop the
Production.ProductCategory,
Production.ProductSubcategory, and
Production.Product tables onto the Object Relational Designer from the
Tables node in Server Explorer.
The next step is to create an ASP.NET page that uses the LinqDataSource control to create CRUD capabilities on top of the
Product table in the AdventureWorks database. Create a new ASP.NET page named
CRUD_Example.aspx and modify its code as follows:
<%@ Page Language="C#" %>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Using LinqDataSource Control for Create, Read, Update and
Delete Operations</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:DetailsView DataSourceID="productSource"
DataKeyNames="ProductID" AutoGenerateEditButton="true"
AutoGenerateDeleteButton="true" AllowPaging="true"
AutoGenerateInsertButton="true" ID="productsView"
runat="server">
</asp:DetailsView>
<asp:LinqDataSource ID="productSource" runat="server"
ContextTypeName="AdventureWorksDatabaseDataContext"
TableName="Products" EnableUpdate="true" EnableInsert="true"
EnableDelete="true">
</asp:LinqDataSource>
</div>
</form>
</body>
</html>
The LinqDataSource control in the preceding code has three properties:
EnableInsert,
EnableUpdate, and
EnableDelete. All three are set to
true to enable automatic insert, update, and delete support. You need to enable the same functionality at the data-bound control,
DetailsView in this case. To accomplish this, you set the
AutoGenerateInsertButton,
AutoGenerateEditButton, and
AutoGenerateDeleteButton of the
DetailsView control to
true. That's all you need to do to enable CRUD operations with the LinqDataSource control.
Figure 1 shows the output produced by navigating to the page in the browser.
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| Figure 1. CRUD-Enabled LinqDataSource Control: After enabling CRUD operations for the LinqDataSource Control data bound to the DetailsView control, the Edit, Delete, and New buttons appear at the bottom of the control. |
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| Figure 2. Editing Data: To enable editing, the control replaces the read-only fields with text boxes where you can enter the product details and adds an Update button that saves changes back to the database. |
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If you click the Edit button in
Figure 1, you'll see the output shown in
Figure 2.
When you click the Update button, the LinqDataSource control automatically retrieves the values from the text boxes and invokes the appropriate methods of the Entity class to update the data in the
Product table.
