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Recipe 7.3 Binding Data to a Web Forms DataListProblemYou need to bind the result set from a query to a DataList control. SolutionSet the DataList's advanced properties as demonstrated by this solution. The schema of table TBL0703 that is used in the solution is shown in Table 7-2.
The Web Forms page sample code defines the DataList control and the three templates—SelectedItemTemplate, ItemTemplate, and EditItemTemplate—which control the display of data for selected items, unselected items, and items being edited. The static Eval( ) method of the DataBinder class is used to fill the field values in each template. Container.DataItem specifies the container argument for the method which when used in a list in a template resolves to DataListItem.DataItem. The code for the Web Forms page is shown Example 7-5. Example 7-5. File: ADOCookbookCS0703.aspx<asp:DataList id="dataList" style="Z-INDEX: 102; LEFT: 16px;
POSITION: absolute; TOP: 56px" runat="server">
<SelectedItemTemplate>
<asp:Button id="editButton" runat="server" Text="Edit"
CommandName="Edit">
</asp:Button>
<B>
<%# DataBinder.Eval(Container.DataItem, "Id") %>;
<%# DataBinder.Eval(Container.DataItem, "IntField") %>;
<%# DataBinder.Eval(Container.DataItem, "StringField") %>
</B>
</SelectedItemTemplate>
<ItemTemplate>
<asp:Button id="selectButton" runat="server" Text="Select"
CommandName="Select">
</asp:Button>
<%# DataBinder.Eval(Container.DataItem, "Id") %>;
<%# DataBinder.Eval(Container.DataItem, "IntField") %>;
<%# DataBinder.Eval(Container.DataItem, "StringField") %>
</ItemTemplate>
<EditItemTemplate>
<asp:Button id="updateButton" runat="server" Text="Update"
CommandName="Update">
</asp:Button>
<asp:Button id="deleteButton" runat="server" Text="Delete"
CommandName="Delete">
</asp:Button>
<asp:Button id="cancelButton" runat="server" Text="Cancel"
CommandName="Cancel">
</asp:Button>
<BR>
<asp:Label id="Label1" runat="server">ID: </asp:Label>
<asp:TextBox id="idTextBox" runat="server" Width="96px"
ReadOnly="True"
Text='<%# DataBinder.Eval(Container.DataItem, "Id") %>'>
</asp:TextBox>
<BR>
<asp:Label id="Label2" runat="server">IntField: </asp:Label>
<asp:TextBox id="intFieldTextBox" runat="server"
Text='<%# DataBinder.Eval(Container.DataItem,
"IntField") %>'>
</asp:TextBox>
<BR>
<asp:Label id="Label3" runat="server">StringField: </asp:Label>
<asp:TextBox id="stringFieldTextBox" runat="server"
Text='<%# DataBinder.Eval(Container.DataItem,
"StringField") %>'>
</asp:TextBox>
</EditItemTemplate>
</asp:DataList>
The code-behind contains six event handlers and three methods:
The C# code for the code-behind is shown in Example 7-6. Example 7-6. File: ADOCookbookCS0703.aspx.cs// Namespaces, variables, and constants
using System;
using System.Configuration;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
private const String TABLENAME = "TBL0703";
// . . .
private void Page_Load(object sender, System.EventArgs e)
{
if(!Page.IsPostBack)
{
dataList.DataSource = CreateDataSource( );
dataList.DataKeyField = "Id";
dataList.DataBind( );
}
}
private DataTable CreateDataSource( )
{
DataTable dt = new DataTable(TABLENAME);
// Create the DataAdapter and fill the table using it.
SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM " + TABLENAME +
" ORDER BY Id",
ConfigurationSettings.AppSettings["DataConnectString"]);
da.Fill(dt);
da.FillSchema(dt, SchemaType.Source);
// Store data in session variable to store data between
// posts to server.
Session["DataSource"] = dt;
return dt;
}
private DataTable UpdateDataSource(DataTable dt)
{
// Create a DataAdapter for the update.
SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM " + TABLENAME +
" ORDER BY Id",
ConfigurationSettings.AppSettings["DataConnectString"]);
// Create a CommandBuilder to generate update logic.
SqlCommandBuilder cb = new SqlCommandBuilder(da);
// Update the data source with changes to the table.
da.Update(dt);
// Store updated data in session variable to store data between
// posts to server.
Session["DataSource"] = dt;
return dt;
}
private void BindDataList( )
{
// Get the data from the session variable.
DataView dv = ((DataTable)Session["DataSource"]).DefaultView;
// Bind the data view to the data list.
dataList.DataSource = dv;
dataList.DataBind( );
}
private void dataList_CancelCommand(object source,
System.Web.UI.WebControls.DataListCommandEventArgs e)
{
// Set the index of the item being edited out of range.
dataList.EditItemIndex = -1;
BindDataList( );
}
private void dataList_DeleteCommand(object source,
System.Web.UI.WebControls.DataListCommandEventArgs e)
{
// Get the data from the session variable.
DataTable dt = (DataTable)Session["DataSource"];
// Get the ID of the row to delete.
int id = (int)dataList.DataKeys[e.Item.ItemIndex];
// Delete the row from the table.
dt.Rows.Find(id).Delete( );
// Update the data source with the changes to the table.
UpdateDataSource(dt);
// Set the index of the item being edited out of range.
dataList.EditItemIndex = -1;
BindDataList( );
}
private void dataList_EditCommand(object source,
System.Web.UI.WebControls.DataListCommandEventArgs e)
{
// Set the index of the selected item out of range.
dataList.SelectedIndex = -1;
// Set the index of the item being edited to the current record.
dataList.EditItemIndex = e.Item.ItemIndex;
BindDataList( );
}
private void dataList_ItemCommand(object source,
System.Web.UI.WebControls.DataListCommandEventArgs e)
{
// Check if the "select" button is pressed.
if (e.CommandName == "Select")
{
// Set the index of the item being edited out of range.
dataList.EditItemIndex = -1;
// Set the index of the selected item to the current record.
dataList.SelectedIndex = e.Item.ItemIndex;
BindDataList( );
}
}
private void dataList_UpdateCommand(object source,
System.Web.UI.WebControls.DataListCommandEventArgs e)
{
// Get the data from the session variable.
DataTable dt = (DataTable)Session["DataSource"];
// Get the ID of the row to update.
int id = (int)dataList.DataKeys[e.Item.ItemIndex];
// Get the DataRow to update using the ID.
DataRow dr = dt.Rows.Find(id);
// Get the column values for the current record from the DataList.
dr["IntField"] =
Int32.Parse(((TextBox)e.Item.FindControl("intFieldTextBox")).Text);
dr["StringField"] =
((TextBox)e.Item.FindControl("stringFieldTextBox")).Text;
// Update the data source with the changes to the table.
UpdateDataSource(dt);
// Set the index of the item being edited out of range.
dataList.EditItemIndex = -1;
BindDataList( );
}
DiscussionThe DataList Web Forms control displays tabular data from a data source and controls the formatting using templates and styles. The DataList must be bound to a data source such as a DataReader, DataSet, DataTable, or DataView—any class that implements the IEnumerable interface can be bound. The easiest way to create a DataList control is to drag the DataList control onto the web page design surface. The DataList Web Form control uses templates to display items, control layout, and provide functional capabilities. Table 7-3 describes the different templates for the DataList.
To format the templates, right-click on the DataList control on the design surface and select one of the three editing submenus of the Edit Template menu. To end editing, right-click the DataList control and select End Template Editing. Templates can also be customized by editing the HTML directly. One of the item templates must contain a data bound control for the DataList control to render at runtime. A Button, LinkButton, or ImageButton web server control can be added to the control templates. These buttons can let the user switch between the different item modes, for example. The buttons bubble their events to the containing DataList control. The events that the DataList raises in response to button clicks on the list items are described in Table 7-4.
After the properties appropriate to the control are set, call the DataBind( ) method of the control or of the page to bind the data source to the server control. |
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