How to Find ListBox1.SelectedItem in other ListBox2 Items

I want to filtering Items of one list and show result into another list. when i fill first ListBox by calling .Items.Add() it works fine. but when i fill it by a table by .DataSource property of it, it works fine too but i can not save .selectedItem of first list and select it in second listbox.

I have ListBox1 in my form and fill it by a table returned from database on Form_Load event.

i also have a button that write on Button_Click event:

            //saving selected item by user in the first 开发者_如何学CList
        object selectedItem = listBox1.SelectedItem;

        // filtering rows in the first List and showing into second List
        DataTable dtable = (DataTable)listBox1.DataSource;
        var x = (from drow in dtable.AsEnumerable()
                 where drow["name"].ToString().ToUpper().StartsWith(textBox1.Text.ToUpper())
                 select drow).AsEnumerable();
        listBox2.DataSource = null;
        if (x.Count() > 0)
            listBox2.DataSource = x.CopyToDataTable();
        listBox2.DisplayMember = listBox1.DisplayMember;
        listBox2.ValueMember = listBox1.ValueMember;

        //setting the selected item in the second list
        if (selectedItem != null && listBox2.Items.Contains(selectedItem))
            listBox2.SelectedItem = selectedItem;

but in result, ListBox2 wont select selected item in ListBox1 because last if would not be true.

please tell me what is wrong. thanks

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I found solution:

 //setting the selected item in the second list
 if (selectedItem != null)
  listBox2.SelectedItem = (
    from item in listBox2.Items.Cast<DataRowView>()
    where item[listBox2.ValueMember].ToString() == ((DataRowView)selectedItem)[listBox1.ValueMember].ToString()
    select item).FirstOrDefault();

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Your problem is the use of method CopyToDataTable. If you read it's summary:

Returns a System.Data.DataTable that contains copies of the System.Data.DataRow objects, given an input System.Collections.Generic.IEnumerable object where the generic parameter T is System.Data.DataRow.

This implies that at the time of your 'if' comparison listBox2.Items contains different instances (with same information) than contained in listbox1.DataSource - this includes listbox1.SelectedItem and therefore listbox2.Items never contains listbox1.SelectedItem.

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The selectedItem object of listBox1 will not be in listBox2. This is due to the line listBox2.DataSource = x.CopyToDataTable() which creates a new list. The two listbox are pointing to the same datasource but they are represented in each listbox with completely different ListItems.

A solution to this is to just iterate the listBox2 and search for the selected item.