如何在ASP.NET 2.0中自定义DataList编辑界面？

<ItemTemplate>
 <h4>
 <asp:Label ID="ProductNameLabel" runat="server"
  Text='<%# Eval("ProductName") %>' />
 </h4>
 <table border="0">
 <tr>
  <td class="ProductPropertyLabel">Category:</td>
  <td class="ProductPropertyValue">
  <asp:Label ID="CategoryNameLabel" runat="server"
   Text='<%# Eval("CategoryName") %>' />
  </td>
  <td class="ProductPropertyLabel">Supplier:</td>
  <td class="ProductPropertyValue">
  <asp:Label ID="SupplierNameLabel" runat="server"
   Text='<%# Eval("SupplierName") %>' />
  </td>
 </tr>
 <tr>
  <td class="ProductPropertyLabel">Discontinued:</td>
  <td class="ProductPropertyValue">
  <asp:Label ID="DiscontinuedLabel" runat="server"
   Text='<%# Eval("Discontinued") %>' />
  </td>
  <td class="ProductPropertyLabel">Price:</td>
  <td class="ProductPropertyValue">
  <asp:Label ID="UnitPriceLabel" runat="server"
   Text='<%# Eval("UnitPrice", "{0:C}") %>' />
  </td>
 </tr>
 <tr>
  <td colspan="4">
  <asp:Button runat="Server" ID="EditButton"
   Text="Edit" CommandName="Edit" />
  </td>
 </tr>
 </table>
 <br />
</ItemTemplate>

<EditItemTemplate>
 <h4>
 <asp:Label ID="ProductNameLabel" runat="server"
  Text='<%# Eval("ProductName") %>' />
 </h4>
 <table border="0">
 <tr>
  <td class="ProductPropertyLabel">Name:</td>
  <td colspan="3" class="ProductPropertyValue">
  <asp:TextBox runat="server" ID="ProductName" Width="90%" />
  <asp:RequiredFieldValidator ID="RequiredFieldValidator1"
   ControlToValidate="ProductName"
   ErrorMessage="You must enter a name for the product."
   runat="server">*</asp:RequiredFieldValidator>
  </td>
 </tr>
 <tr>
  <td class="ProductPropertyLabel">Category:</td>
  <td class="ProductPropertyValue">
  <asp:DropDownList ID="Categories" runat="server"
   DataSourceID="CategoriesDataSource"
   DataTextField="CategoryName" DataValueField="CategoryID" />
  </td>
  <td class="ProductPropertyLabel">Supplier:</td>
  <td class="ProductPropertyValue">
  <asp:DropDownList ID="Suppliers" DataTextField="CompanyName"
   DataSourceID="SuppliersDataSource"
   DataValueField="SupplierID" runat="server" />
  </td>
 </tr>
 <tr>
  <td class="ProductPropertyLabel">Discontinued:</td>
  <td class="ProductPropertyValue">
  <asp:CheckBox runat="server" id="Discontinued" />
  </td>
  <td class="ProductPropertyLabel">Price:</td>
  <td class="ProductPropertyValue">
  <asp:Label ID="UnitPriceLabel" runat="server"
   Text='<%# Eval("UnitPrice", "{0:C}") %>' />
  </td>
 </tr>
 <tr>
  <td colspan="4">
  <asp:Button runat="Server" ID="UpdateButton" CommandName="Update"
   Text="Update" />
   
  <asp:Button runat="Server" ID="CancelButton" CommandName="Cancel"
   Text="Cancel" CausesValidation="False" />
  </td>
 </tr>
 </table>
 <br />
 <asp:ObjectDataSource ID="CategoriesDataSource" runat="server"
 OldValuesParameterFormatString="original_{0}" SelectMethod="GetCategories"
 TypeName="CategoriesBLL">
 </asp:ObjectDataSource>
 <asp:ObjectDataSource ID="SuppliersDataSource" runat="server"
 OldValuesParameterFormatString="original_{0}" SelectMethod="GetSuppliers"
 TypeName="SuppliersBLL">
 </asp:ObjectDataSource>
</EditItemTemplate>

protected void Products_EditCommand(object source, DataListCommandEventArgs e)
{
 // Set the DataList's EditItemIndex property and rebind the data
 Products.EditItemIndex = e.Item.ItemIndex;
 Products.DataBind();
}
protected void Products_CancelCommand(object source, DataListCommandEventArgs e)
{
 // Return to DataList to its pre-editing state
 Products.EditItemIndex = -1;
 Products.DataBind();
}

protected void Products_UpdateCommand(object source, DataListCommandEventArgs e)
{
 // Make sure the page is valid...
 if (!Page.IsValid)
 return;
 // Read in the ProductID from the DataKeys collection
 int productID = Convert.ToInt32(Products.DataKeys[e.Item.ItemIndex]);
 // Read in the product name and price values
 TextBox productName = (TextBox)e.Item.FindControl("ProductName");
 DropDownList categories = (DropDownList)e.Item.FindControl("Categories");
 DropDownList suppliers = (DropDownList)e.Item.FindControl("Suppliers");
 CheckBox discontinued = (CheckBox)e.Item.FindControl("Discontinued");
 string productNameValue = null;
 if (productName.Text.Trim().Length > 0)
 productNameValue = productName.Text.Trim();
 int categoryIDValue = Convert.ToInt32(categories.SelectedValue);
 int supplierIDValue = Convert.ToInt32(suppliers.SelectedValue);
 bool discontinuedValue = discontinued.Checked;
 // Call the ProductsBLL's UpdateProduct method...
 ProductsBLL productsAPI = new ProductsBLL();
 productsAPI.UpdateProduct(productNameValue, categoryIDValue, supplierIDValue,
    discontinuedValue, productID);
 // Revert the DataList back to its pre-editing state
 Products.EditItemIndex = -1;
 Products.DataBind();
}

<asp:DropDownList ID="Categories" DataSourceID="CategoriesDataSource"
 DataTextField="CategoryName" DataValueField="CategoryID" runat="server"
 SelectedValue='<%# Eval("CategoryID") %>' AppendDataBoundItems="True">
 <asp:ListItem Value=" Selected="True">(None)</asp:ListItem>
</asp:DropDownList>
...
<asp:DropDownList ID="Suppliers" DataSourceID="SuppliersDataSource"
 DataTextField="CompanyName" DataValueField="SupplierID" runat="server"
 SelectedValue='<%# Eval("SupplierID") %>' AppendDataBoundItems="True">
 <asp:ListItem Value=" Selected="True">(None)</asp:ListItem>
</asp:DropDownList>

int? categoryIDValue = null;
if (!string.IsNullOrEmpty(categories.SelectedValue))
 categoryIDValue = Convert.ToInt32(categories.SelectedValue);
int? supplierIDValue = null;
if (!string.IsNullOrEmpty(suppliers.SelectedValue))
 supplierIDValue = Convert.ToInt32(suppliers.SelectedValue);