SDF file convert into CSV access denied

private void button2_Click(object sender, EventArgs e)
        {
            
            SqlCeConnection conn = null;
            SqlCeCommand cmd = null;
            SqlCeDataReader rdr = null;


            try
            { 
                <code>System.IO.TextWriter stm = new System.IO.StreamWriter(new System.IO.FileStream(@"C:\Users\Name\Desktop\...\...\Columba\Columba-XT-Standard-20180710155851", System.IO.FileMode.Create), Encoding.Default)</code>;
                while (rdr.Read())
                {
                    for (int i = 0; i < rdr.FieldCount - 2; i++)
                    {
                        if (rdr[i] != null)
                        {
                            stm.Write(rdr[i].ToString());
                            stm.Write(";");
                        }
                        else
                        {
                            stm.Write(";");
                        }
                    }
                    if (rdr[rdr.FieldCount - 1] != null)
                    {
                        stm.Write(rdr[0].ToString());
                    }
                    stm.Write(System.Environment.NewLine);
                }
                stm.Close();

                rdr.Close();

                cmd.Dispose();
            }
            finally
            {
                conn.Close();
            }
            
            
        }