private void SelectAllProvButton_Click(object sender, EventArgs e)
 {
     for (int i = 0; i < ProviderCheckedListBox.Items.Count; i++)
     {
         ProviderCheckedListBox.SetItemChecked(i, true);
     }
 }
 private void ClearAllButton_Click(object sender, EventArgs e)
 {
     for (int i = 0; i < ProviderCheckedListBox.Items.Count; i++)
     {
         if (ProviderCheckedListBox.GetItemChecked(i))
         {
             ProviderCheckedListBox.SetItemChecked(i, false);
         }
     }
 }