C# brisanje file-a

Imam problema sa brisanjem file-a, odnosno SQL baze. Dobijem grešku da se ona još koristi.
Malo sam googlao i vidio da bi trebao staviti pooling na false. To sam i napravio u connection string-u, ali nije pomoglo.

Ima tko kavku ideju?

                    System.Net.WebClient Baza = new System.Net.WebClient();
                    Baza.DownloadFile("http://dl.dropbox.com/u/14208/ABC.mdf", "C:\\ABC.mdf");
                    Baza.DownloadFile("http://dl.dropbox.com/u/14208/ABC_log.ldf", "C:\\ABC_log.ldf");

                    System.Data.SqlClient.SqlConnection con;
                    con = new System.Data.SqlClient.SqlConnection();
                    con.ConnectionString ="Data        Source=.\\SQLEXPRESS;AttachDbFilename=C:\\ABC.mdf;IntegratedSecurity=True;            
                    Pooling=False;Connect Timeout=30;User Instance=True";

                    DataSet ds1;
                    ds1 = new DataSet();
                    System.Data.SqlClient.SqlDataAdapter da;

                    string sql = "SELECT * From ABC";
                    da = new System.Data.SqlClient.SqlDataAdapter(sql, con);
                   
                    con.Open();
                    da.Fill(ds1, "ABC");
                    int MaxRow = ds1.Tables["ABC"].Rows.Count;
                    try
                    {
                        int i = 0;
                        for (i = 0; i < MaxRow; i++)
                        {
                            DataRow dRow = ds1.Tables["ABC"].Rows[i];
                            if (textbox1.Text.ToString() == dRow.ItemArray.GetValue(1).ToString() && textbox2.Text.ToString() ==
                            dRow.ItemArray.GetValue(2).ToString())
                            {
                                MessageBox.Show("OK");
                            }
                            else
                            {
                                MessageBox.Show("False");                               
                            }
                        }                        
                    }
                    catch { }

                    con.Close();
                    con.Dispose();;                  
                    System.IO.File.Delete("C:ABC.mdf");
                    System.IO.File.Delete("C:ABC_og.ldf");                 
                }

                catch
                {}
            }    
        } 
    }
}

Jel ovo web ili Win Forms Aplikacija?

fali ti backslash. tribalo bi bit ovako

System.IO.File.Delete(@"C:\ABC.mdf");

System.IO.File.Delete(@"C:\ABC_og.ldf");