This step-by-step article describes how to use the ItemDataBound event of the Web Forms DataGrid, DataList, and Repeater controls to perform special processing on individual rows of data that are displayed in a data-bound list control.
When you display a list of items in a data-bound list control, you may want to apply conditional logic to display different information, or to apply different formatting, to different items. You can use the ItemDataBound event to apply this logic as each individual row of data is processed and displayed.
Add code in the Page_Load event to retrieve the list of customers from the sample Northwind database into a SqlDataReader object. Bind the Repeater control to the DataReader. Adjust the connection string that is listed in the following code to connect to an available SQL Server:
Dim cn As SqlConnection = New SqlConnection("Data Source=(local);" & _ "Initial Catalog=Northwind;User ID=user;Password=password") cn.Open() Dim cmd As SqlCommand = New SqlCommand("SELECT * FROM Customers", cn) Dim dr As SqlDataReader = cmd.ExecuteReader() Repeater1.DataSource = dr Repeater1.DataBind()
Run the project. A bulleted list of contact names from the Northwind Customers list is displayed on the page. Each contact name is formatted in blue by default.
Switch back to HTML view for the Web Form. In the opening <asp:Repeater> tag, add the following attribute to set an event handler for the ItemDataBound event:
Switch back to Code view, and then add the following event handler procedure:
Protected Sub FormatRepeaterRow(ByVal sender As Object, ByVal e As RepeaterItemEventArgs) If e.Item.ItemType = ListItemType.Item Or _ e.Item.ItemType = ListItemType.AlternatingItem Then Dim dbr As DbDataRecord = CType(e.Item.DataItem, DbDataRecord) If Not IsDBNULL(dbr("Country")) AndAlso dbr("Country") = "USA" Then CType(e.Item.FindControl("lblContactName"), Label).ForeColor = _ System.Drawing.Color.Red End If End IfEnd Sub
Run the project again. Contacts from the United States (13 of the 91 customers) are displayed in red because of the conditional formatting code that is contained in the ItemDataBound event handler.
If the data source is a DataReader object, you must cast e.Item.DataItem as type DBDataRecord (from System.Data.Common) in the event handler. If the data source is a DataTable, you must cast e.Item.DataItem as type DataRowView.
Even if you have not created an <AlternatingItemTemplate> entry in your Repeater control, every other row still has an ItemType value of ListItemType.AlternatingItem. Therefore, you must look for both ListItemType.Item and ListItemType.AlternatingItem to process every row.