Foreach doesn't go through all items?

I have this code:

       foreach (var item in ListView1.Items)
          开发者_StackOverflow社区  {
                ListView1.Items.Remove(item);
                ListView21.Items.Add(item);
            }

the loop stops at half of the items?

Any idea?

EDIT

Well, maybe it's my mistake, I need to clarify that this is UltraListView control from Infrajistics, where I can't add item to another list unless I remove it or clone it from the original list.

But thanks, most of the comments regarding do not modify the list within the loop were correct, so this code works:

           foreach (var item in listView1.Items)
            {
                var i = item.Clone(true);
                listView2.Items.Add(i);
            }
            listView1.Items.Clear();

Thanks,

You cannot modify iterated collection, it should die with exception (or in undefined behavior). Try making a copy of the array:

   foreach (var item in ListView1.Items.ToArray())
   {
       ListView1.Items.Remove(item);
       ListView21.Items.Add(item);
   }

EDIT:

in fact, your example code can be achieved by writing:

ListView21.Items.AddRange(ListView1.Items);
ListView1.Items.Clear();

(which in fact isn't EXACTLY what you are doing, but gives the same result and I think it won't bother you having the same content in both listviews for a moment). The latter is supported since .NET2.0, first solution requires linq, and therefore .NET3.5.

You are modifying the collection you are looping through. Try using a for statement from top to bottom (from the item with the highest index to 0).

for (int i = ListView1.Items.Count - 1; i >= 0; i--)
{
    var item = ListView1.Items[i];
    ListView1.Items.Remove(item);
    ListView21.Items.Insert(0, item);
}

It will cause a runtime exception, complaining that you cannot modify the collection while iterating through it. You have to use for loop instead.

for(int index = Items.Count; index > 0; index--)
{
    .......
    // use Add and RemoveAt
}

EDIT : As mentioned by others. If you just need to move items from one collection to the other. AddRange and Clear will be better.

Do you get any exception or error message? Looping in a collection and remove items from the same collection is always a bad idea.

This looks like the WinForms list view control, so:

ListViewItem[] items = ListView1.Items.ToArray();
ListView1.Items.Clear();
ListView21.Items.AddRange(items);

Why just not CopyTo() to new list and then Clear() items?

You are looping through all items, removing all of them, then adding them to another list. As others have commented, you cannot remove items from a list in a for-each. Why not looping through all items to add them to your other list, and then remove them all in one go?

foreach (var item in ListView1.Items)
{
    ListView21.Items.Add(item);
}
ListView1.Items.Clear();   // remove all

PS: is this an ASP.NET listview or a WinForms listview?

That's because you're changing the collection inside the loop. Use a normal for loop as follows:

for(int i=0; i < ListView1.Items.Count-1; i++)
{
       ListView21.Items.Add(ListView1.Items[i]);
       ListView1.Items.RemoveAt(i);
}