Simple Thoughts on Everything

<form id="form1" runat="server">
<asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString="<%$ ConnectionStrings:NORTHWNDConnectionString %>"
  SelectCommand="SELECT [EmployeeID], [LastName], [FirstName], [Title] FROM [Employees]">
</asp:SqlDataSource>
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="EmployeeID"
  DataSourceID="SqlDataSource1" OnRowDataBound="GridView1_RowDataBound">
  <Columns>
      <asp:TemplateField HeaderText="EmployeeID" InsertVisible="False" SortExpression="EmployeeID">
          <EditItemTemplate>
              <asp:SqlDataSource ID="SqlDataSource2" runat="server"
               ConnectionString="<%$ ConnectionStrings:NORTHWNDConnectionString %>"
                  SelectCommand="SELECT [OrderID], [ShipName] FROM [Orders] WHERE ([EmployeeID] = @EmployeeID)">
                  <SelectParameters>
                      <asp:Parameter Name="EmployeeID" Type="Int32" />
                  </SelectParameters>
              </asp:SqlDataSource>
              <asp:DropDownList ID="DropDownList1" runat="server" DataSourceID="SqlDataSource2"
                  DataTextField="ShipName" DataValueField="OrderID">
              </asp:DropDownList>
          </EditItemTemplate>
          <ItemTemplate>
              <asp:Label ID="Label1" runat="server" Text='<%# Bind("EmployeeID") %>'></asp:Label>
          </ItemTemplate>
      </asp:TemplateField>
      <asp:BoundField DataField="LastName" HeaderText="LastName" ReadOnly="True" SortExpression="LastName" />
      <asp:BoundField DataField="FirstName" HeaderText="FirstName" ReadOnly="True" SortExpression="FirstName" />
      <asp:BoundField DataField="Title" HeaderText="Title" ReadOnly="True" SortExpression="Title" />
      <asp:TemplateField>
          <EditItemTemplate>
              update
          </EditItemTemplate>
          <ItemTemplate>
              <asp:LinkButton ID="LinkButton1" runat="server" CommandName="Edit">Edit</asp:LinkButton>
          </ItemTemplate>
      </asp:TemplateField>
  </Columns>
</asp:GridView>
</form>

public partial class test_dataSource : System.Web.UI.Page
{
  protected void Page_Load(object sender, EventArgs e)
  {

  }
  protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
  {
      //只對datarows作用
      if (e.Row.RowType == DataControlRowType.DataRow)
      {
          //判斷是否是編輯欄..因為gridview還有分單雙所以要多加Alternamte
          if (e.Row.RowState == DataControlRowState.Edit ||
              e.Row.RowState == (DataControlRowState.Edit | DataControlRowState.Alternate))
          {
              //把sqldatasource餵值
              string id = GridView1.DataKeys[e.Row.RowIndex][0].ToString();
              ((SqlDataSource)e.Row.FindControl("SqlDataSource2")).
                  SelectParameters["EmployeeID"].DefaultValue = id;
          }
      }
  }
}