Its not possible to set(check) many items at a time like this, checkedListBox1.CheckedItems = list;
better you can use for loop like:
List<tableClass> list = MyCheckedList();
for (int count = 0; count < checkedListBox1.Items.Count; count++)
{
if (list.Contains(checkedListBox1.Items[count].ToString()))
{
checkedListBox1.SetItemChecked(count, true);
}
}