ASP.NET Web Controls , DropDownList items disappearing after 2 postbacks

1. DropDownList with Postback on only one item...

2. determining a dropdownlist selected item without doing a postback - ASP.NET Web Controls

3. DataGrid item dropdownlist javascript disable

Hello all,.
I have a datagrid and one of the columns has a static dropdownlist
which means each column has the exact same dropdownlist.  On the c#
side values are pulled from the database and depending on the value
from the db it should either keep the dropdownlist enabled or it should
set it as disabled for that row.  I believe some javascript like
document.getElementById would help somehow but I'm still learning.

Eg.
Each row has a color list of:

BROWN
BLUE
ORANGE

if the database says that the row value is null then disable & hide
that column for that row.  Meaning that item doesn't need a color.

If someone could help that would be great.  Thanks in advance.

4. Disable databound dropdownlist if 0 items - ASP.NET Web Controls

5. Disab;e selection of dropdownlist items (in a GridView)

Is there an example of using client side script to disable selection of some 
items in a drop down that I could follow.

It would seem tricky as there are multiple drop downs in the GridView.  I 
would need to remember the last selected value for each drop down within the 
grid.  If the selected value is not permitted then reset to the remembered 
value.

And then when a valid item is selected the remebered value for that drop 
down would need to be updated.

Are there any links or examples that I could utilise?

6. DropDownList Disabled Items in the list - Asp.Net

7. DropDownList 2 always returns Selected = 0 for all items - even selected item

Hi All

I have 2 DropDownList boxes on a page.

The first (id= "Operation") is populated on PageLoad with the contents
of a database table.
The second id="WorkStations" will not be populated until the first has
been changed
The definitions are below.

<ASP:DropDownList id="Operation"
      runat="server"
      AppendDataBoundItems="True"
      AutoPostBack="True"
     OnSelectedIndexChanged="Operation_SelectedIndexChanged">
</ASP:DropDownList>  

<ASP:DropDownList id="WorkStations"
      runat="server"
      AppendDataBoundItems="True"
      AutoPostBack="True"
      OnSelectedIndexChanged="WorkStations_SelectedIndexChanged">
</ASP:DropDownList>  
.
Both events fire successfully - on every item change.

When I change the Operation box it fires correctly and the WorkStations
box is populated correctly. However when I select an item in the
WorkStations box none of the items are listed as Selected in the event
handler. The event fires - I am using Delphi Developer Studio 2006 to
develop and I have debugged the event handler - and the dropdownlist
box is being picked up.

The 2 event handlers are

protected void Operation_SelectedIndexChanged(object sender, EventArgs
e)
  {
  OleDbConnection conoper = new OleDbConnection("provider=IBMDA400;Data
Source=xx.xxx.xx.xxx;User Id=xxxxxxx;password=xxxxxxxxxx");
  OleDbCommand cmdoper = new OleDbCommand();
  string LString;

  foreach(ListItem item in Operation.Items)  // This is dropdownlist
box 1
    {
	if(item.Selected)
	{
	if (item.Value == "Please Select An Operation")
	{
	LString = "<script language=JavaScript>alert('No Operation Selected.
\n Please Select An Operation');</script>";
		RegisterStartupScript("startupScript", LString);
		}
	else
		{
		LString = "<script language=JavaScript>alert('" + item.Value +
"');</script>";
		conoper.Open();
		cmdoper.Connection = conoper;
		cmdoper.CommandType = CommandType.Text;
		LString = "select * from WRKINSTRUC.WORKSTATN Where OPERNAME = '" +
item.Value + "'";
		cmdoper.CommandText =  LString;
		OleDbDataReader dsWorkCenters = cmdoper.ExecuteReader();
		WorkStations.DataSource = dsWorkCenters;
		WorkStations.DataTextField = "WORKSTATN";
		WorkStations.DataValueField = "WORKSTATN";
		WorkStations.DataBind();
		conoper.Close();
		WorkStations.Items.Insert(0, new ListItem("Please Select A
Workstation", "0"));
		WorkStations.SelectedIndex = 0;
		}
	}
   }
}

protected void WorkStations_SelectedIndexChanged(object sender,
EventArgs e)  // This is dropdownlist box 2
  {
  string LString;
  int indexNum;
  indexNum = WorkStations.SelectedIndex;
  Response.Write(indexNum );

  foreach(ListItem item in WorkStations.Items)
  {
  if(item.Selected)
	{
	if (item.Value == "Please Select A Workstation")
		{
		LString = "<script language=JavaScript>alert('No Workstation
Selected. \n Please Select A Workstation');</script>";
		RegisterStartupScript("startupScript", LString);
		}
	else
		{
		LString = "<script language=JavaScript>alert('" + item.Text +
"');</script>";
		RegisterStartupScript("startupScript", LString);
		}
	}
}
}


As I am new to C# and ASP.NET could anyone please give me an idea of
what is going wrong here

Thanks in advance for any assistance offered

Iain

8. Controls added dynamically disappears after postback - Asp.Net