select all items in listview faster

What actually is taking so much time? Is it your loop itself (I do believe 30000 iterations last not that long) or are there additional actions slowing the process? You could try to disable event handlers (ItemSelectionChanged and the like, all that may be triggered by selection) or call SuspendLayout()/ResumeLayout() methods before and after selection. Also, if you really have to deal with 30000 items, consider using listview in virtual mode

Disabling event handlers is easy: for example, you do have ItemSelectionChanged handler, listView1_SelectedIndexChanged on your listview, listView1. Then selection logic should look like that:

listView1.SelectedIndexChanged-=listView1_SelectedIndexChanged;

try
{
 // selection loop
}
finally
{
  listView1.SelectedIndexChanged+=new EventHandler(listView1_SelectedIndexChanged);
}

Try/catch block is not necessary, it's added simply to ensure event handler will be restored no matter what, even after exception in loop. If there are more handlers, ItemSelectionChanged, for example, just disable and restore them in the same manner.

Working with layout events suspending is simple as well. Improving previous block of code:

listView1.SelectedIndexChanged-=listView1_SelectedIndexChanged;
listView1.SuspendLayout();

try
{
 // selection loop
}
finally
{
  listView1.SelectedIndexChanged+=new EventHandler(listView1_SelectedIndexChanged);
  listView1.ResumeLayout();
}

Finally, placing listview in virtual mode doesn't even require code :). You can do it from Property Editor, setting VirtualMode property to true (by default it's false). Working with listview this way is harder, though: you have to implement RetrieveVirtualItem event handler and provide VirtualListSize property; also you cannot use Items/SelectedItems collections. There are other limitations as well (see here), so you should decide yourself whether virtual mode suits your project

Check out A Much Easier to Use ListView[^].

It has a ListView called FastObjectListView that can build a list of 10,000 objects in less than 0.1 seconds.

Your user never needs so many items at a time. The view should be virtualized. Disagree? Can you explain the use case when all the items are really needed?

—SA

OP wrote:

I have about 30,000 items, and its taking long time to select.

It's horrible man.....use paging in result. Load on demand is the best way.

For your reference

SQL Server 2005 Paging Results[^]

Mostly this happen because of event which gets fired after each item is selected. looping through 10,000 will not have impact. So following logic can be implemented
1) Before entering loop remove event handler

this.definitionList.ItemCheck -= new System.Windows.Forms.ItemCheckEventHandler(this.definitionList_ItemCheck);



2) process loop

3) restore event hander again

this.definitionList.ItemCheck += new System.Windows.Forms.ItemCheckEventHandler(this.definitionList_ItemCheck);

4) Add code if you need to do some extra thing on "Select event" which were happening in event handler..

Good Luck
Satish