Check all item in listview with huge list item?

Question

I want to check about 3000 item in listview. This is a bit of code :

foreach (ListViewItem item in this.lvItem.Items)
{
    item.Checked = !item.Ch         


        

Answer 1

I heard a rumor that for large list items a for loop will work faster than a foreach loop try

for(int i = 0; i = < this.1vItem.Items.Count; i++)
{
//Stuff
}

Answer 2

for (int i = 0; i <= listView1.Items.Count - 1; i++)
{
     if (!listView1.Items[i].Checked)
     listView1.Items[i].Checked = true;
}

Answer 3

Will something like this work for you? ...when checked, add the items to a Dictionary ...when unchecked, remove from the Dictionary. Not tested code but wondering if you could do something like this:

Dictionary<String, ListViewItem> Dic = listView.Items 
    .Cast<ListViewItem>() 
    .ToDictionary(x => x.Text, x => x.SubItems[0].Checked); 

You asked how to better go about it. What I am saying is on your Check Event you will want to add items to your list view. I doubt that a user will actually check all 3000, so change your code to decide how you would want to handle checked items, the example that I have given you uses Lambda expression. If not familiar, then please alter your question to reflect what it is that you actually need and/or want...

Answer 4

I also don't think it's wise to expect a user to click 3000 items. But something I did recently, when adding the items, knowing that there would never be many and by default they should be checked, is check the items before adding them to the list.

Something like this:

foreach (Recipient recipient in recipients)
{
    var item = new ListViewItem(recipient.FirstName + " " + recipient.LastName);
    item.Tag = recipient;
    item.Checked = true;
    lvRicipients.Items.Add(item);
}

Answer 5

I had the same problem but I found why.

I had an "ItemChecked" event handler attached to my listView that was doing some heavy stuff.

I removed the eventHandler and it solved my problem. Try removing any "ItemChecked" eventhandler and see if the speed is better.

Answer 6

You need to call BeginUpdate before the loop and EndUpdate after the loop:

listView1.BeginUpdate();
foreach (ListViewItem item in listView1.Items)
    item.Checked = true;
listView1.EndUpdate();

Calling BeginUpdate prevents the control from drawing until the EndUpdate method is called.