Button update for DropDownList added dinamically in GridView

Question

Hello everybody. I find myself in difficulty and ask for help for a situation that is often treated, but separately, namely: DDL dynamically created in GridView and event external to GridView that takes some in value / Text ... x stored in the DB.

They are at the first experiences and the code I report often derives from something else found on the net.

************************************************** 

In a WebForm I drew a GridView. Outside the GridView is a Button.

The GridView is made up of 2 BoundFields (of which the first is not visible).

This is the page:

<% @ Page Title = "" Language = "C #" MasterPageFile = "~ / Site.Master" AutoEventWireup = "true" CodeBehind = "WebForm2.aspx.cs" Inherits = "ScheduleWeb.WebForm2"%>

<asp: Content ID = "Content1" ContentPlaceHolderID = "HeadContent" runat = "server">

</ asp: Content>

<asp: Content ID = "Content2" ContentPlaceHolderID = "MainContent" runat = "server">

<% - <asp: Panel ID = "panel1" runat = "server" Height = "100px" Width = "930px" ScrollBars = "Horizontal"> -%>

<asp: GridView ID = "GridView2" runat = "server" DataKeyNames = "Codice_fiscale" OnRowDataBound = "GridView_RowDataBound" Width = "938px" AutoGenerateColumns = "False" Font-Names = "Arial" Font-Size = "Smaller" OnRowCreated "GridView2_RowCreated">

<Columns>

<asp: BoundField DataField = "code_fiscale" HeaderText = "code_fiscale" ItemStyle-Width = "280px" ReadOnly = "True" SortExpression = "code_fiscale" Visible = "False">

<ItemStyle Width = "280px"> </ItemStyle>

</ asp: BoundField>

<asp: BoundField DataField = "Surname_Name" HeaderText = "Surname and Name" ItemStyle-Width = "180px" ReadOnly = "True" SortExpression = "Surname_Name">

<ControlStyle Width = "180px" />

<ItemStyle Wrap = "False"> </ItemStyle>

</ asp: BoundField>

</Columns>

<EditRowStyle Font-Names = "Arial" Font-Size = "Small" />

</ asp: GridView>

<% - </ asp: Panel> -%>

& nbsp; _______________________________________________________________________________________ <br />

& nbsp; <br />

<asp: Button ID = "ButtonOK" runat = "server" Text = "Remember" OnClick = "ButtonOK_Click" />

<asp: Label ID = "Label2" runat = "server" BackColor = "# FF6600" Text = "Label"> </ asp: Label>

<br />

</ asp: Content>

*********************************

In the page Load:

1. I "assume" n°2 DateTime variables that I will need to add the DropDownLists

2. "populate" the mysql oCombo DataTable that I will need for the combos

3. if (! This.IsPostBack) {

... "populate" the DataTable oDataTable_2 by filtering my table by x credentials and date range

... loop this DT x generate the TemplateFields. This is the code:

     for (int k = 2; k <oDataTable_2.Columns.Count; k ++) // add the day columns from the third column

     {

         TemplateField tfield = new TemplateField ();

         tfield = new TemplateField ();

         tfield.HeaderText = oDataTable_2.Columns [k] .ColumnName;

         tfield.ItemStyle.Width = 55;

         GridView2.Columns.Add (tfield);

      }

... I do the DataBind

}

4. This is the code:

protected void GridView_RowDataBound (Object sender, GridViewRowEventArgs e)

{

   if (e.Row.RowType == DataControlRowType.DataRow)

   {

      string NomeGiorno = "";

      for (int k = 2; k <oDataTable_2.Columns.Count; k ++)

      {

         NomeGiorno = oDataTable_2.Columns [k] .ColumnName.ToString ();

         DropDownList ddlCombo = new DropDownList ();

         ddlCombo.ID = NomeGiorno;

         ddlCombo.DataSource = oCombo;

         ddlCombo.DataTextField = oCombo.Columns [0] .ColumnName;

         ddlCombo.DataValueField = oCombo.Columns [0] .ColumnName;

         ddlCombo.DataBind ();

         string country = (e.Row.DataItem as DataRowView) .Row [DayName] .ToString ();

         ddlCombo.Width = 55;

         ddlCombo.Font.Name = "Arial";

         ddlCombo.Font.Size = 8;

         ddlCombo.Items.FindByText (country) .Selected = true;

         e.Row.Cells [k] .Controls.Add (ddlCombo);

      }

   }

GridView2.Columns [1] .HeaderStyle.CssClass = "locked";

}

So far everything ok (or at least outwardly). I use DDL, combining items ... everything OK!

But later I want to store the new situation in the DB and so I will have to build

the update query by cycling the columns of the GridView (which has only one row)

But I can't find control !!

I tried this code ...

protected void ButtonOK_Click (object sender, EventArgs e)

{

      string cStringa = "update schedule set";

      string NomeGiorno = "";

      for (int k = 2; k <GridView2.Columns.Count; k ++) // loop the day columns from the third column

      {// ie after tax code, surname and name.

         NomeGiorno = GridView2.Columns [k] .ToString ();

         string test = ((DropDownList) GridView2.Rows [0] .FindControl (NomeGiorno)). SelectedItem.Text;

         .....

         .....

      }

} 

I get the classic error:

System.NullReferenceException: 'Reference to an object not set on an object instance.'

Thanks to all those x will be able to give me a hand

Alessio