how get directories read only ? c#

Question

 i use this code to select a path and get all subdirectories of it 

if (FBD_devis.ShowDialog() == DialogResult.OK)
{
    try
    {

        DirectoryInfo diri_info = new DirectoryInfo(FBD_devis.SelectedPath);             listBox2.Items.AddRange(diri_info.GetDirectories("*", SearchOption.AllDirectories));

    }
    catch (UnauthorizedAccessException u)
    {   MessageBox.Show("le problème c'est a cause ce Dossiers: " + u.Message + "\n" + u.Source);

    }
}

 but when i select the path

 

 

 

it generate this problem 

 

how can I fix this problem please ?