How to create TextBox2_TextChanged put into Edit template

Question

Hi Guys

Please help me

This is textbox in EditItem template in gridview :

 

<EditItemTemplate>

<asp:TextBox ID="TextBox11" Width="80" runat="server" Text='<%# Bind("Service_Start_Date", "{0:dd/MM/yyyy}") %>' TargetControlID="TextBox11"></asp:TextBox>

<ajaxToolkit:CalendarExtender ID="CalendarExtender1" TargetControlID="TextBox11" runat="server" Format="dd/MM/yyyy" />

</EditItemTemplate>

 

and this is other :

 

<EditItemTemplate>

<asp:TextBox ID="TextBox11" Width="80" runat="server" Text='<%# Bind("Service_Start_Date", "{0:dd/MM/yyyy}") %>' TargetControlID="TextBox12"></asp:TextBox>

<ajaxToolkit:CalendarExtender ID="CalendarExtender1" TargetControlID="TextBox11" runat="server" Format="dd/MM/yyyy" />

</EditItemTemplate>

 

How to applied this code and how declare txt in gridview 

 

protected void TextBox11_TextChanged(object sender, EventArgs e)

{

string date = TextBox11.Text;

DateTime dt1 = DateTime.ParseExact(date, "dd/MM/yyyy", CultureInfo.InvariantCulture);

TextBox12.Text = dt1.AddDays(30).ToString("dd/MM/yyyy");

Label1.BackColor = Color.Green;

Label2.Text = ("Team Should Be Changed On:" + dt1.AddDays(30).ToShortDateString());

}

 

thanks