Here is the sample code. The only trick is that you need to load those dynamic controls again after post back. Otherwise, you won't be able to access those.
<asp:PlaceHolder runat="server" ID="PlaceHolder1"></asp:PlaceHolder>
<asp:Button runat="server" ID="AddButton" OnClick="AddButton_Click" Text="Add" />
private List<int> _controlIds;
private List<int> ControlIds
{
get
{
if (_controlIds == null)
{
if (ViewState["ControlIds"] != null)
_controlIds = (List<int>)ViewState["ControlIds"];
else
_controlIds = new List<int>();
}
return _controlIds;
}
set { ViewState["ControlIds"] = value; }
}
private List<string> DataSource
{
get { return new List<string> { "One", "Two", "Three" }; }
}
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack)
{
var dataSource = DataSource;
foreach (int id in ControlIds)
{
var ddl = new DropDownList();
ddl.ID = id.ToString();
foreach (var data in dataSource)
ddl.Items.Add(new ListItem(data));
PlaceHolder1.Controls.Add(ddl);
}
}
}
protected void AddButton_Click(object sender, EventArgs e)
{
var dataSource = DataSource;
for (int i = 0; i < 3; i++)
{
var reqs = ControlIds;
int id = ControlIds.Count + 1;
reqs.Add(id);
ControlIds = reqs;
var ddl = new DropDownList();
ddl.ID = id.ToString();
foreach (var data in dataSource)
ddl.Items.Add(new ListItem(data));
PlaceHolder1.Controls.Add(ddl);
}
}
