Dymanically added user controls disapper on postback in asp.net

Question

I have a asp.net listbox which is populated in Page_Load event if it is not postback. Whenever users selects any item from the asp.net listbox, I need to load usercontrols based upon how many items were selected from the listbox. I have been able to load multiple controls; however, my problem is those newly added controls get disapper on postback.

Here is my sample code

 if (!this.IsPostback)
    {
bindListBox();

    }

private void bindListBox()
{
lstAgenyList .DataSource = GetAgenyList();
lstAgenyList.DataTextField = "Id";
lstAgenyList.DataValueField = "Name";
lstAgenyList.DataBind();
}

protected void lstAgenyList_OnSelectedIndexChanged(object sender, EventArgs e)
{

foreach(Item in lstAgenyList.items) {
if(item.Selected)
{
addControls(item.Text, item.Value);
}
}

}

private void addControls(string itemName, string itemValue)
{
var control = this.LoadControl("~/Controls/a.ascx");
control.id= itemName.Trim() + itemValue + "Controls_";
this.agenyListPlaceHolder.Controls.add(control);

}

So my questons to you guys, what are the best options for implementing logic like this in asp.net web form.

Answer 1

It has to do with PlaceHolder and dynamically added controls.

Answer to almost the same question is here: http://forums.asp.net/t/1623719.aspx

Basically, everyting in placeholder will be lost upon post back and you have to re-add it back into it during PreInit event from hidden fields, Request.Form, or ViewState.

Answer 2

控件消失是因为维护动态添加的控件的状态是我们的责任，您想尝试一下占位符 。