DBHelper 数据库帮助类

     /// <summary>
     /// 数据库帮助类
     /// <author>vito</author>
     /// </summary>
     public class DBHelper
     {
           
  8
         /// <summary>
         /// 数据库连接字符串
         /// </summary>
         private string connStr = System.Configuration.ConfigurationManager.AppSettings["connStr"].ToString();

         /// <summary>
         /// 一个有效的数据库连接对象
         /// </summary>
         private SqlConnection _MyConnection;
         public SqlConnection MyConnection
         {
             get
             {
                 if(_MyConnection == null)
                 {
                     _MyConnection = new SqlConnection(connStr);
                 }
                 return _MyConnection;
             }
         }

         /// <summary>
         /// 返回受影响行数
         /// </summary>
         /// <param name="cmdText">SQL语句</param>
         /// <param name="commandParameters">参数集</param>
         /// <returns></returns>
         public int MyExecuteNonQuery(string cmdText, params SqlParameter[] commandParameters)
         {
             int result = ;
             SqlCommand cmd = new SqlCommand();
             SqlConnection conn = MyConnection;
             try
             {
                 PrepareCommand(cmd, conn, null, cmdText, commandParameters);
                 result = cmd.ExecuteNonQuery();
             }
             catch(SqlException ex)
             {
                 throw new Exception(ex.Message);
             }
             finally
             {
                 cmd.Parameters.Clear();
             }
             return result;
         }

         /// <summary>
         /// 返回DataSet
         /// </summary>
         /// <param name="cmdText">SQL语句</param>
         /// <param name="commandParameters">参数集</param>
         /// <returns></returns>
         public DataSet MyExecuteDataset(string cmdText, params SqlParameter[] commandParameters)
         {
             DataSet ds = new DataSet();
             SqlConnection conn = MyConnection;
             SqlCommand cmd = new SqlCommand();
             PrepareCommand(cmd, conn, null, cmdText, commandParameters);
             using (SqlDataAdapter da = new SqlDataAdapter(cmd))
             {
                 try
                 {
                     da.Fill(ds);
                 }
                 catch (SqlException ex)
                 {
                     throw new Exception(ex.Message);
                 }
                 finally
                 {
                     cmd.Parameters.Clear();
                 }
             }
             return ds;
         }

         /// <summary>
         /// 返回DataReader (使用后请关闭DataReader)
         /// </summary>
         /// <param name="cmdText">SQL语句</param>
         /// <param name="commandParameters">参数集</param>
         /// <returns></returns>
         public SqlDataReader MyExecuteReader(string cmdText, params SqlParameter[] commandParameters)
         {
             SqlConnection conn = MyConnection;
             SqlCommand cmd = new SqlCommand();
             try
             {
                 PrepareCommand(cmd,conn,null,cmdText,commandParameters);
                 SqlDataReader myReader = cmd.ExecuteReader(CommandBehavior.CloseConnection);//关闭DataReader的同时，Connection也将同时关闭
                 return myReader;
             }
             catch(SqlException ex)
             {
                 throw new Exception(ex.Message);
             }
             finally
             {
                 cmd.Parameters.Clear();
             }
         }

         /// <summary>
         /// 返回首行首列的值
         /// </summary>
         /// <param name="cmdText">SQL语句</param>
         /// <param name="commandParameters">参数集</param>
         /// <returns></returns>
         public object MyExecuteScalar(string cmdText,params SqlParameter[] commandParameters)
         {
             SqlConnection conn = MyConnection;
             SqlCommand cmd = new SqlCommand();
             try
             {
                 PrepareCommand(cmd,conn,null,cmdText,commandParameters);
                 return cmd.ExecuteScalar();
             }
             catch(SqlException ex)
             {
                 throw new Exception(ex.Message);
             }
             finally
             {
                 cmd.Parameters.Clear();
             }
         }

         /// <summary>
         /// 设置SqlCommand
         /// </summary>
         /// <param name="cmd">执行对象</param>
         /// <param name="conn">连接对象</param>
         /// <param name="trans">事务</param>
         /// <param name="cmdText">SQL语句</param>
         /// <param name="cmdParms">参数集</param>
         private void PrepareCommand(SqlCommand cmd, SqlConnection conn, SqlTransaction trans, string cmdText, SqlParameter[] cmdParms)
         {
             if (conn.State != ConnectionState.Open)
                 conn.Open();
             cmd.Connection = conn;
             cmd.CommandText = cmdText;
             if (trans != null)
                 cmd.Transaction = trans;
             cmd.CommandType = CommandType.Text;
             if (cmdParms != null)
             {
                 foreach (SqlParameter parameter in cmdParms)
                 {
                     if ((parameter.Direction == ParameterDirection.InputOutput || parameter.Direction == ParameterDirection.Input) && (parameter.Value == null))
                     {
                         parameter.Value = DBNull.Value;
                     }
                     cmd.Parameters.Add(parameter);
                 }
             }
         }
     }