Wie ein Listenfeld dynamisch in ASP.Net erstellen

Question

protected override void OnInit(EventArgs e) 
    { 
     ListBox lst = new ListBox(); 

     lst.Attributes["class"] = "cat-list"; 

     lst.DataSource = cat.list(Convert.ToInt32(0)); 
     lst.DataTextField = "catName"; 
     lst.DataValueField = "catId"; 
     lst.DataBind(); 


     lst.AutoPostBack = true; 
     lst.SelectedIndexChanged += Lst_SelectedIndexChanged; 

     Panel pnl = new Panel(); 
     pnl.Attributes["class"] = "col-sm-2 col-xs-12"; 
     pnl.Controls.Add(lst); 

     categories.Controls.Add(pnl); 
    } 

    private void Lst_SelectedIndexChanged(object sender, EventArgs e) 
    { 
     ListBox listBox = (ListBox)sender; 
     ListBox lst = new ListBox(); 

     lst.Attributes["class"] = "cat-list"; 

     lst.DataSource = cat.list(Convert.ToInt32(listBox.SelectedValue)); 
     lst.DataTextField = "catName"; 
     lst.DataValueField = "catId"; 
     lst.DataBind(); 


     lst.AutoPostBack = true; 
     lst.SelectedIndexChanged += Lst_SelectedIndexChanged; 

     Panel pnl = new Panel(); 
     pnl.Attributes["class"] = "col-sm-2 col-xs-12"; 
     pnl.Controls.Add(lst); 

     categories.Controls.Add(pnl); 
    } 

Die erste Listbox selectedindexchanged Veranstaltung arbeiten, aber zweiten Listbox selectedindexchanged Ereignis nicht funktioniert. Wenn ich eine Option in der zweiten Listbox auswähle, wird die zweite Listbox verloren. Halten Sie die ausgewählte Option in der ersten Listbox. Was kann ich dagegen tun? Bitte hilf mir.

Answer 1

Ich hoffe, dass Ihnen helfen

Panel pnl = new Panel(); 
    ListBox lst1 = new ListBox(); 
    ListBox lst2 = new ListBox(); 
    ListBox lst3 = new ListBox(); 

    protected override void OnInit(EventArgs e) 
    { 
     lst1.Attributes["class"] = "cat-list"; 
     lst1.AutoPostBack = true; 
     lst1.SelectedIndexChanged += Lst_SelectedIndexChanged; 

     lst2.Attributes["class"] = "cat-list"; 
     lst2.AutoPostBack = true; 
     lst2.SelectedIndexChanged += Lst_SelectedIndexChanged; 
     lst2.Visible = false; 

     lst3.Attributes["class"] = "cat-list"; 
     lst3.AutoPostBack = true; 
     lst3.SelectedIndexChanged += Lst3_SelectedIndexChanged; 
     lst3.Visible = false; 

     pnl.Attributes["class"] = "col-sm-2 col-xs-12"; 
     pnl.Controls.Add(lst1); 
     pnl.Controls.Add(lst2); 
     pnl.Controls.Add(lst3); 
     categories.Controls.Add(pnl); 
    } 

    protected void Page_Load(object sender, EventArgs e) 
    { 
     if (!IsPostBack) 
     { 
      lst1.DataSource = cat.list(Convert.ToInt32(0)); 
      lst1.DataTextField = "catName"; 
      lst1.DataValueField = "catId"; 
      lst1.DataBind(); 
     } 
    } 

    private void Lst_SelectedIndexChanged(object sender, EventArgs e) 
    { 
     ListBox listBox = (ListBox)sender; 
     ListBox lst; 
     if (listBox == lst1) 
      lst = lst2; 
     else 
      lst = lst3; 

     lst.DataSource = cat.list(Convert.ToInt32(listBox.SelectedValue)); 
     lst.DataTextField = "catName"; 
     lst.DataValueField = "catId"; 
     lst.DataBind(); 

     lst.Visible = true; 
    } 
    private void Lst3_SelectedIndexChanged(object sender, EventArgs e) 
    { 
     //your code for third Listbox 
    }