Thursday, March 22, 2012

The first intem in a DropDownList is vanishing!

The first intem in a DropDownList is vanishing!
My code to load a DropDownList is shown below. Yet when I load the
page after a postback there is no zeroth item present.
lstManager.Items.Clear();
lstManager.DataSource = _dsData.Tables["manager"].DefaultView;
lstManager.DataValueField = "ManagerID";
lstManager.DataTextField = "Name";
lstManager.DataBind();
lstManager.Items.Insert(0, new ListItem("none", "0"));
There's nothing special about the control definition:
<asp:DropDownList ID="lstManager" runat="server" Height="20px"
Width="250px" />
What's going on here?
This was the old code I replaced. Why does the old code (below) work
and why is my new code (above) broke?
lstManager.Items.Clear();
ListItem li = new ListItem("none","0");
lstManager.Items.Add(li);
foreach (DataRow drManager in _dsData.Tables["manager"].Rows)
{
ListItem liManager = new ListItem((string)drManager["Name"],
((int)drManager["ManagerID"]).ToString());
lstManager.Items.Add(liManager);
}I had this one a while back; turns out I was using simple properties
on a Master Page that required a DataBind() call to bind them. When
it was called, it was also rebinding the content page, which loses the
manually added items.
I recall this issue also happened with an ASCX file on the page, or if
you call a generic DataBind() any time after the addition of
ListItems, etc.
Dunc
http://www.fluidfoundation.com
On 1 Jun, 15:24, mark4asp <mark4...@.gmail.com> wrote:
> The first intem in a DropDownList is vanishing!
> My code to load a DropDownList is shown below. Yet when I load the
> page after a postback there is no zeroth item present.
> lstManager.Items.Clear();
> lstManager.DataSource = _dsData.Tables["manager"].DefaultView;
> lstManager.DataValueField = "ManagerID";
> lstManager.DataTextField = "Name";
> lstManager.DataBind();
> lstManager.Items.Insert(0, new ListItem("none", "0"));
> There's nothing special about the control definition:
> <asp:DropDownList ID="lstManager" runat="server" Height="20px"
> Width="250px" />
> What's going on here?
> This was the old code I replaced. Why does the old code (below) work
> and why is my new code (above) broke?
> lstManager.Items.Clear();
> ListItem li = new ListItem("none","0");
> lstManager.Items.Add(li);
> foreach (DataRow drManager in _dsData.Tables["manager"].Rows)
> {
> ListItem liManager = new ListItem((string)drManager["Name"],
> ((int)drManager["ManagerID"]).ToString());
> lstManager.Items.Add(liManager);
> }
On 1 Jun, 16:30, Dunc <duncan.we...@.gmail.com> wrote:
> I had this one a while back; turns out I was using simple properties
> on a Master Page that required a DataBind() call to bind them. When
> it was called, it was also rebinding the content page, which loses the
> manually added items.
> I recall this issue also happened with an ASCX file on the page, or if
> you call a generic DataBind() any time after the addition of
> ListItems, etc.
> Dunchttp://www.fluidfoundation.com
> On 1 Jun, 15:24, mark4asp <mark4...@.gmail.com> wrote:
>
>
>
>
>
>
>
>
>
>
>
>
>
> - Show quoted text -
Thanks Dunc, for sharing that with me - that scenario you described
sounds very like mine.

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