DBhelper异常求高人解决 在线等

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<connectionStrings>
<add name="connString" connectionString="Data Sourse=.;Initial Catalog=NetBarMIS;uid=xjqaini;pwd=237711"/>
</connectionStrings>
</configuration>
上面数据库链接
namespace NetBarMIS.Cls
{
  class DBHelper
  {
  private static string sConn = System.Configuration.ConfigurationManager.ConnectionStrings["connString"].ToString();
  private static SqlConnection conn = new SqlConnection(sConn);

  /// <summary>
  /// 打开数据库连接
  /// </summary>
  public static void Open()
  {
  if (conn.State == ConnectionState.Closed)
  {
  conn.Open();
  }
  }
  /// <summary>
  /// 关闭数据库连接
  /// </summary>
  public static void Close()
  {
  if (conn.State == ConnectionState.Open)
  {
  conn.Close();
  }
  }
  /// <summary>
  /// Scalar方法
  /// </summary>
  /// <param name="sql"></param>
  /// <returns></returns>
  public static object ExecuteScalar(string sql)
  {
  object obj = null;
  SqlCommand comm = new SqlCommand(sql, conn);

  try
  {
  Open();
  obj = comm.ExecuteScalar();
  }
  catch
  {

  throw;
  }
  finally
  {
  Close();
  }
  return obj;
  }
  /// <summary>
  /// NonQuery方法
  /// </summary>
  /// <param name="sql"></param>
  /// <returns></returns>
  public static int ExecuteNonQuery(string sql)
  {
  int iResult;
  SqlCommand comm = new SqlCommand(sql, conn);

  try
  {
  Open();
  iResult = comm.ExecuteNonQuery();
  }
  catch
  {

  throw;
  }
  finally
  {
  Close();
  }
  return iResult;
  }
  /// <summary>
  /// Reader方法
  /// </summary>
  /// <param name="sql"></param>
  /// <returns></returns>
  public static SqlDataReader ExecuteReader(string sql)
  {
  SqlDataReader dr;
  SqlCommand comm = new SqlCommand(sql, conn);
  try
  {
  Open();
  dr = comm.ExecuteReader();
  }
  catch
  {

  throw;
  }
  return dr;
  }
  /// <