Question

I have ListBox called lstProductGroups.

On a simple Windows Form, a method called GetGroups gives me string groups selected by the user like Cars, Bikes etc.

public List<string> GetGroups()
{
    List<string> prodGroups = (from object item in lstProductGroups.SelectedItems select item.ToString()).ToList();

    return prodGroups;
}

But if I try to access same method from another thread I get all items in my list called System.Data.DataRowView.

I even tried it in a foreach loop with BeginInvoke, but the item.ToString() always returns System.Data.DataRowView.

I am new to Winforms with threading. What am I doing wrong?

Answer 1

First declare a delegate:

delegate List<string> GetItemsDlg();

Change your method like this:

List<string> GetGroups() {
    if (lstProductGroups.InvokeRequired) {
        var dlg = new GetItemsDlg(GetGroups);
        return lstProductGroups.Invoke(dlg) as List<string>;
    }
    List<string> prodGroups = (from object item in lstProductGroups.SelectedItems select item.ToString()).ToList();

    return prodGroups;

}

Call your method:

List<string> items = GetGroups();