Forms Data Controls :: There Is Already A Component Named ".." Component Must Have A Unique Name

i got a problem.. how i can declare template textbox in a datagrid at code behind? i already make a stored procedure and put the update query inside it.. if i declare the textbox inside code behind(.aspx.vb).. there will be an error.. " there is already a component named "txtitem1"component must have a unique name.."

Dim con As New SqlConnection(ConfigurationSettings.AppSettings("ConnectionString1"))
Dim cmd As New SqlCommand
Dim sda As New SqlDataAdapter
cmd.CommandType = CommandType.StoredProcedure
cmd.CommandText = "ETendering3"
cmd.Parameters.Add("@item", SqlDbType.NVarChar).Value = txtitem1.Text
cmd.Parameters.Add("@price", SqlDbType.Decimal).Value = txtprice1.Text
cmd.Parameters.Add("@remark", SqlDbType.NVarChar).Value = txtremark1.Text
cmd.Parameters.Add("@consump", SqlDbType.Decimal).Value = txtconsump1.Text
cmd.Parameters.Add("@value", SqlDbType.Decimal).Value = txtvalue1.Text
cmd.Connection = con
Try
con.Open()
DataGrid12.DataSource = cmd.ExecuteReader()
DataGrid12.DataBind()
Finally
con.Close()
End Try
con.Dispose()
cmd.Dispose()
con = Nothing
cmd = Nothing
_______________________________________________________
.aspx
<Columns>
<asp:BoundColumn DataField="Listing_Id" HeaderText="Listing"></asp:BoundColumn>
<asp:BoundColumn DataField="No" HeaderText="No"></asp:BoundColumn>
<asp:BoundColumn DataField="Item_Category" HeaderText="Category"></asp:BoundColumn>
<asp:TemplateColumn HeaderText="Description">
<ItemTemplate>
<asp:TextBox id=TextBox1 runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.Item_Description") %>'>
</asp:TextBox>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox id="txtitem1" runat="server"></asp:TextBox>
</EditItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn HeaderText="Price" FooterText=" 10/50">
<ItemTemplate>
<asp:TextBox id=TextBox3 runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.Price") %>'>
</asp:TextBox>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox id="txtprice1" runat="server"></asp:TextBox>
</EditItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn HeaderText="Remarks">
<ItemTemplate>
<asp:TextBox id=TextBox2 runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.Remark") %>'>
</asp:TextBox>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox id="txtremark1" runat="server"></asp:TextBox>
</EditItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn HeaderText="Consumption">
<ItemTemplate>
<asp:TextBox runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.Consumption") %>'>
</asp:TextBox>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox runat="server" ID="txtconsump1"></asp:TextBox>
</EditItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn HeaderText="Value">
<ItemTemplate>
<asp:TextBox runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.Value") %>'>
</asp:TextBox>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox runat="server" ID="txtvalue1"></asp:TextBox>
</EditItemTemplate>
</asp:TemplateColumn>
</Columns>