Login authentication fails

public override bool ValidateUser(string username, string password)
        {
            using(SqlConnection  conn = new SqlConnection(m_strDBConnection))
            {
                try
                {
                    /* Create command */
                    SqlCommand  command = new SqlCommand("SELECT [Encode],[USERNAME],[PASSWORD]  FROM [dbo].[Users]" + "WHERE [USERNAME]='" + username + "' AND [PASSWORD]='" + password + "'", conn);
                    
                    /* Open connection */
                    conn.Open();
               
                    /* Run query */
                    SqlDataReader  reader = command.ExecuteReader();

                    /* Check if we have something */
                    bool bResult = reader.HasRows;
                    AuthenticateEventArgs e = new AuthenticateEventArgs();
                    
                    /* Close connection */
                    conn.Close();
                    
                    return bResult;
                }
                catch(Exception ex)
                {
                    System.Diagnostics.Trace.WriteLine(ex.Message);
                }
                return false;
            }
        }