get value of dynamic control on postback?

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Dave - 03 Aug 2007 04:44 GMT

For simplicity sake,

How do you get the value of selected dropdown on a postback? I understand
for a dynamic control, you need to re-create it on each postback, but how do
I modify the code to grab the SelectedValue?

protected void Page_Load(object sender, EventArgs e)
{
DropDownList list = new DropDownList();
list.ID = "DropDownList1";
list.Items.Add(new ListItem("1", "One"));
list.Items.Add(new ListItem("2", "Two"));
list.Items.Add(new ListItem("3", "Three"));
PlaceHolder1.Controls.Add(list);
}

Reply to this Message

Manish Bafna - 03 Aug 2007 06:02 GMT

Hi,
So, the controls that were dynamically created are no longer there and
consequently the values returned from these controls have no place to go.
They are lost in the viewstate.

In order to catch these values the dynamically generated controls needs to
be re-generated at Page_Load. The important thing is to assign the same ID to
each control. The ViewState uses the ID property of the Control objects to
reinstate the values.

If you create a dynamic dropdownlist, conditionally, say in response to some
other control's click event. Then, on PostBack, you recreate a "new" dropdown
with the same object name, then "magically" that new dropdown becomes the
dynamically-created dropdown. You get all of the user-initiated and
code-generated properties.
ref:http://www.codeproject.com/aspnet/retainingstate.asp?df=100&forumid=14609&exp=0&
select=1495875

Signature

Hope this answers your question.
Thanks and Regards.
Manish Bafna.
MCP and MCTS.

> For simplicity sake,
>
[quoted text clipped - 11 lines]
> PlaceHolder1.Controls.Add(list);
> }

Reply to this Message

Eliyahu Goldin - 03 Aug 2007 07:21 GMT

Place the code for control creting in the PreInit event. The reason is
because LoadViewState occurs between Init and Load events.

Signature

Eliyahu Goldin,
Software Developer & Consultant
Microsoft MVP [ASP.NET]
http://msmvps.com/blogs/egoldin

> For simplicity sake,
>
[quoted text clipped - 11 lines]
> PlaceHolder1.Controls.Add(list);
> }

Reply to this Message

get value of dynamic control on postback?

Free Magazines