Gridview中的编辑模板与项模板的用法

  <asp:GridView ID="GridView1" AutoGenerateColumns="false" runat="server" BorderColor="Black"
             onrowcancelingedit="GridView1_RowCancelingEdit"
             onrowediting="GridView1_RowEditing"
             onrowdatabound="GridView1_RowDataBound" onrowupdating="GridView1_RowUpdating">
             <Columns>
                 <asp:TemplateField HeaderText ="ID">
                     <ItemTemplate>
                         <%#Eval("CustomerID") %>
                     </ItemTemplate>
                     <EditItemTemplate>
                     <%#Eval("CustomerID") %>
                     </EditItemTemplate>
                 </asp:TemplateField>
                 <asp:TemplateField HeaderText ="Name">
                     <ItemTemplate>
                         <%#Eval("CompanyName") %>
                     </ItemTemplate>
                     <EditItemTemplate>
                         <asp:TextBox ID="TextBox1" runat="server" Text ='<%#Eval("CompanyName") %>'></asp:TextBox>
                     </EditItemTemplate>
                 </asp:TemplateField>
                 <asp:TemplateField HeaderText ="Contact">
                     <ItemTemplate>
                         <%#Eval("ContactName") %>
                     </ItemTemplate>
                     <EditItemTemplate>
                         <asp:TextBox ID="TextBox2" runat="server" Text ='<%#Eval("ContactName") %>'></asp:TextBox>
                     </EditItemTemplate>
                 </asp:TemplateField>
                 <asp:TemplateField HeaderText ="Address">
                     <ItemTemplate>
                         <%#Eval("Address") %>
                     </ItemTemplate>
                     <EditItemTemplate>
                         <asp:TextBox ID="TextBox3" runat="server" Text ='<%#Eval("Address") %>'></asp:TextBox>
                     </EditItemTemplate>
                 </asp:TemplateField>
                 <asp:TemplateField HeaderText ="City">
                     <ItemTemplate>
                         <%#Eval("City") %>
                     </ItemTemplate>
                     <EditItemTemplate>
                         <asp:DropDownList ID="DropDownList1" AutoPostBack="true" runat="server">
                         </asp:DropDownList>
                     </EditItemTemplate>
                 </asp:TemplateField>
                 <asp:TemplateField HeaderText ="编辑">
                     <ItemTemplate>
                         <asp:Button ID="Button1" runat="server" Text="编辑" CommandName="Edit" />
                     </ItemTemplate>
                     <EditItemTemplate>
                         <asp:Button ID="Button2" runat="server" Text="修改" CommandName="Update" />&nbsp;
                         <asp:Button ID="Button3" runat="server" Text="取消" CommandName="Cancel" />
                     </EditItemTemplate>
                 </asp:TemplateField>
             </Columns>
         </asp:GridView>

 protected void Page_Load(object sender, EventArgs e)
     {
         if (!IsPostBack)
         {
             databind();
         }
     }
     public void databind()
     {
         SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["Conn"].ToString());
         SqlCommand cmd = new SqlCommand("SELECT * FROM CUSTOMERS", con);
         SqlDataAdapter da = new SqlDataAdapter(cmd);
         DataSet ds = new DataSet();
         da.Fill(ds);
         this.GridView1.DataSource = ds.Tables[];
         this.GridView1.DataKeyNames = new string[] { "CustomerID", "City" };
         this.GridView1.DataBind();
     }
     protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
     {
         this.GridView1.EditIndex = e.NewEditIndex;
         databind();
     }
     protected void GridView1_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
     {
         this.GridView1.EditIndex = -;
         databind();
     }
     protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
     {
         foreach (TableCell item in e.Row.Cells)
         {
             item.Attributes.Add("style", "border-color:black");

         }
         if (e.Row.RowType == DataControlRowType.DataRow)
         {
             DropDownList dr = (DropDownList)e.Row.FindControl("DropDownList1");
             if (dr != null)
             {
                 SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["Conn"].ToString());
                 SqlCommand cmd = new SqlCommand("Select distinct City  from Customers", con);
                 SqlDataAdapter da = new SqlDataAdapter(cmd);
                 DataSet ds = new DataSet();
                 da.Fill(ds);
                 dr.DataSource = ds.Tables[];
                 dr.DataTextField = "City";
                 dr.DataValueField = "City";
                 dr.DataBind();
                 dr.SelectedItem.Text = this.GridView1.DataKeys[e.Row.RowIndex].Values[].ToString();
             }
         }
     }
     protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
     {
         SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["Conn"].ToString());
         SqlCommand cmd = new SqlCommand("Update Customers set CompanyName=@CompanyName,ContactName=@ContactName,City=@City where CustomerID=@CustomerID", con);
         SqlParameter[] ps = new SqlParameter[];
         ps[] = new SqlParameter("@CompanyName",SqlDbType.NVarChar,);
         ps[] = new SqlParameter("@ContactName",SqlDbType.NVarChar,);
         ps[] = new SqlParameter("@City",SqlDbType.NVarChar,);
         ps[] = new SqlParameter("@CustomerID",SqlDbType.NChar,);
         ps[].Value = ((TextBox)this.GridView1.Rows[e.RowIndex].FindControl("TextBox1")).Text.Trim();
         ps[].Value = ((TextBox)this.GridView1.Rows[e.RowIndex].FindControl("TextBox2")).Text.Trim();
         ps[].Value = ((DropDownList)this.GridView1.Rows[e.RowIndex].FindControl("DropDownList1")).SelectedItem.Text;
         ps[].Value = this.GridView1.DataKeys[e.RowIndex].Values[];
         cmd.Parameters.AddRange(ps);
         if (con.State == ConnectionState.Closed)
         {
             con.Open();
         }
         cmd.ExecuteNonQuery();
         this.GridView1.EditIndex = -;
         databind();
     }