Listview change applies after 2nd postback? - asp.net

Question

i have a listview and a button out of this list view, on button click i want to add a "insert" row defined in InsertItemTemplate. The problem is when i click the button, this row is added(i know this because when a do any postback aftewards this row really shows), but isnt shown/rendered. So the question is: why this change doesn´t apply on the first postback - button click? here is my code:
EDIT:
Whole Codebehind:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
ListItem ByName = new ListItem("By name", "Name");
ListItem ByPhone = new ListItem("By phone", "Phone");
ListItem ByEmail = new ListItem("By email", "Email");
FilterTypeDDL.Items.Add(ByName);
FilterTypeDDL.Items.Add(ByPhone);
FilterTypeDDL.Items.Add(ByEmail);
FilterTypeDDL.DataBind();
}
}
//protected void ListView_ItemCommand(object sender, ListViewCommandEventArgs e)
//{
//switch (e.CommandName)
//{
//case "EditItem":
// break;
//case "InsertItem":
// if (Page.IsValid)
// {
// string NameTxt = ((TextBox)(ListView.InsertItem.FindControl("NameTextBox"))).Text.Trim();
// string PhoneTxt = ((TextBox)(ListView.InsertItem.FindControl("PhoneTextBox"))).Text.Trim();
// string EmailTxt = ((TextBox)(ListView.InsertItem.FindControl("EmailTextBox"))).Text.Trim();
// DAORestaurant.InsertRestaurant(NameTxt, PhoneTxt, EmailTxt);
// ListView.InsertItemPosition = InsertItemPosition.None;
// ListView.DataSource = DAORestaurant.GetRestaurants();
// ListView.DataBind();
// break;
// }
// break;
//case "CancelCreation":
// ListView.InsertItemPosition = InsertItemPosition.None;
// ListView.DataSource = DAORestaurant.GetRestaurants();
// ListView.DataBind();
// break;
//case "Articles":
// Session["Restaurant"] = e.CommandArgument.ToString();
// Control ArticlesCtrl = LoadControl("~/Controls/Article.ascx");
// ListViewItem Item = (ListViewItem)e.Item;
// Item.FindControl("CtrlPlaceHolder").Controls.Add(ArticlesCtrl);
//}
//}
protected void closeButton_Click(object sender, EventArgs e)
{
}
protected void newArticleButton_Click(object sender, EventArgs e)
{
}
protected void NewRestaurantBtn_Click(object sender, EventArgs e)
{
ListView.InsertItemPosition = InsertItemPosition.LastItem;
//SetDataSource();
//ListView.DataBind();
}
protected void ValidateName(object source, ServerValidateEventArgs args)
{
string NameTxt = ((TextBox)(ListView.InsertItem.FindControl("NameTextBox"))).Text.Trim();
args.IsValid = (NameTxt.Length > 2 && NameTxt.Length < 51);
}
protected void ValidateUniqueness(object source, ServerValidateEventArgs args)
{
string NameTxt = ((TextBox)(ListView.InsertItem.FindControl("NameTextBox"))).Text.Trim();
args.IsValid = DAORestaurant.IsUnique(NameTxt);
}
protected void ValidatePhone(object source, ServerValidateEventArgs args)
{
string PhoneTxt = ((TextBox)(ListView.InsertItem.FindControl("PhoneTextBox"))).Text.Trim();
Regex regex = new Regex(#"^\d{3}\s\d{3}\s\d{3}$");
args.IsValid = regex.IsMatch(PhoneTxt);
}
protected void ValidateEmail(object source, ServerValidateEventArgs args)
{
string EmailTxt = ((TextBox)(ListView.InsertItem.FindControl("EmailTextBox"))).Text.Trim();
Regex regex = new Regex(#"^([\w\.\-]+)#([\w\-]+)((\.(\w){2,3})+)$");
args.IsValid = regex.IsMatch(EmailTxt);
}
protected void ShowAllBtn_Click(object sender, EventArgs e)
{
Session["ALL"] = true;
ListView.DataSource = DAORestaurant.GetRestaurants();
ListView.DataBind();
}
protected void FilterBtn_Click(object sender, EventArgs e)
{
string filterType = FilterTypeDDL.SelectedValue;
string substring = StringTB.Text.Trim().ToUpper();
Session["ALL"] = false;
Session["FilterType"] = filterType;
Session["Substring"] = substring;
ListView.DataSource = DAORestaurant.GetRestaurants(substring, filterType);
ListView.DataBind();
}
protected void ListView_ItemEditing(object sender, ListViewEditEventArgs e)
{
ListView.EditIndex = e.NewEditIndex;
//SetDataSource();
//ListView.DataBind();
}
protected void ListView_ItemInserting(object sender, ListViewInsertEventArgs e)
{
}
protected void ListView_ItemCanceling(object sender, ListViewCancelEventArgs e)
{
if (e.CancelMode == ListViewCancelMode.CancelingInsert)
{
ListView.InsertItemPosition = InsertItemPosition.None;
}
else
{
ListView.EditIndex = -1;
}
//SetDataSource();
//ListView.DataBind();
}
private void SetDataSource()
{
if ((bool)Session["ALL"])
{
ListView.DataSource = DAORestaurant.GetRestaurants();
}
else
{
ListView.DataSource = DAORestaurant.GetRestaurants((string)Session["Substring"], (string)Session["FilterType"]);
}
}
The code commented out is what i used before, i´ve switched to what you can see now, but the problem still persists. Only when i uncomment those 2 commented lines in each event, the changes apply instantly, but i know i cannot use such a method that many times, and it should not even be there.

Answer 1

Because of the order of execution. Try setting it in the Page_Load event:
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack &&
!string.IsNullOrEmpty(Request.Form[NewRestaurantBtn.ClientID]))
{
ListView.InsertItemPosition = InsertItemPosition.LastItem;
}
}