Code Snippet - Selecting an Item in a DataList using C#
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In this article, we will look at a technique that allows us to generate a DataGrid (children data) based on a selection in a DropDownList (parent data).
Basically, when an item is selected in the DropDownList, the page is posted back and we run a query to fill the DataGrid.
The code sample below uses a couple other best pratices you should understand and be aware of:
*The code below uses structured error handling techniques in the form of the Try...Catch statement. Go here
to read more about the great new structured error handling we VBers now have.
*The code below also uses a connection string stored in a web.config configuration file. Go here to read more about
the web.config configuration file and how it can be used to store application wide data.
The Code:
<%@ Page Language="C#" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<html>
<head>
<script language="C#" runat="server">
void Page_Load(Object sender, EventArgs e) {
if (!IsPostBack) {
BindData();
}
}
void BindData() {
SqlConnection myConnection =
new SqlConnection(ConfigurationSettings.AppSettings["DSN_pubs"]);
SqlCommand myCommand =
new SqlCommand("Select title From titles", myConnection);
SqlDataReader myDataReader;
try {
myConnection.Open();
myDataReader = myCommand.ExecuteReader(CommandBehavior.CloseConnection);
MyDataList.DataSource = myDataReader;
MyDataList.DataBind();
}
catch (Exception myException) {
Response.Write("An error has occurred: " + myException.ToString());
}
}
void MyDataList_ItemCommand(Object sender, DataListCommandEventArgs e) {
MyDataList.SelectedIndex = e.Item.ItemIndex;
BindData();
}
</script>
</head>
<body>
<form runat="server" method="post">
<asp:DataList id="MyDataList"
runat="server"
Width="100%"
OnItemCommand="MyDataList_ItemCommand"
RepeatColumns="1">
<ItemTemplate>
<asp:Table Runat="server" Width="100%">
<asp:TableRow>
<asp:TableCell>
<asp:LinkButton id="Select" runat="server" Text="Select" CommandName="Select"/>
<asp:Label runat="server" id="lbltitle">
<%#DataBinder.Eval(Container.DataItem, "title") %>
</asp:Label>
</asp:TableCell>
</asp:TableRow>
</asp:Table>
</ItemTemplate>
<SelectedItemTemplate>
<asp:Table Runat="server" Width="100%">
<asp:TableRow BackColor="Yellow">
<asp:TableCell>
<asp:Label runat="server" id="lbltitle2">
<%#DataBinder.Eval(Container.DataItem, "title") %>
</asp:Label>
</asp:TableCell>
</asp:TableRow>
</asp:Table>
</SelectedItemtemplate >
</asp:DataList>
</form>
</body>
</html>
The Result:
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