Question

How can i use second method instead of first?

first (web user control)

   public void Remove()         {              int count = this.ListBox1.Items.Count;              for (int i = count - 1; i > -1; i--)             {                 if (ListBox1.Items[i].Selected)                 {                     ListBox1.Items.Remove(ListBox1.Items[i]);                 }             }         }

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Test.aspx(Test of first)

  protected void btnRemove_Click(object sender, EventArgs e)         {             ItemOrderer2.Remove();          }

second(web user control)

 public void Remove(string value)         {             ListItem li = new ListItem();             li = ListBox1.Items.FindByValue(value);             if (li != null)             {                 this.ListBox1.Items.Remove(li);             }

Test.aspx( Test of Second)

  protected void btnRemove_Click(object sender, EventArgs e)         {            // ItemOrderer2.Remove();             if (ItemOrderer2.Items.Count > 0)                 foreach (ListItem li in ItemOrderer2.Items)                 {                     if (li.Selected)                     {                         ItemOrderer2.Remove(li.Value);                     }                 }         }

Answer 1

You can’t use foreach if you are removing data inside the foreach – it (intentionally) breaks the iterator.

If for works, why change it? If you are desperate to use foreach, then build a separate list first – for example:

List<ListItem> remove = new List<ListItem>(); foreach(ListItem li in ItemOrdere2.Items) {     if(li.Selected) remove.Add(li); } foreach(ListItem li in remove) {     ItemOrderer2.Remove(li); // or similar } 

The first query can often be simplified by LINQ if if is available.