一个C#访问数据库的帮助类

using System;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Collections;

namespace SQLHelperClass
{

    public abstract class SqlHelper
    {
        public static readonly string ConnectionStringMSSQL = ConfigurationManager.AppSettings["dbPath"].ToString();
        private static Hashtable parmCache = Hashtable.Synchronized(new Hashtable());
        public static int ExecuteNonQuery(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            using (SqlConnection conn = new SqlConnection(connectionString))
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                int val = cmd.ExecuteNonQuery();
                cmd.Parameters.Clear();
                return val;
            }
        }

        public static int ExecuteNonQuery(SqlConnection connection, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {

            SqlCommand cmd = new SqlCommand();

            PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
            int val = cmd.ExecuteNonQuery();
            cmd.Parameters.Clear();
            return val;
        }

        public static int ExecuteNonQuery(SqlTransaction trans, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, trans.Connection, trans, cmdType, cmdText, commandParameters);
            int val = cmd.ExecuteNonQuery();
            cmd.Parameters.Clear();
            return val;
        }


        public static SqlDataReader ExecuteReader(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            SqlConnection conn = new SqlConnection(connectionString);
            try
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                SqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                cmd.Parameters.Clear();
                return rdr;
            }
            catch
            {
                conn.Close();
                throw;
            }
        }
        public static DataSet ExecuteDataSet(string connectionString, string cmdText)
        {
            DataSet __ds = new DataSet();
            try
            {
                SqlDataAdapter sda = new SqlDataAdapter(cmdText, connectionString);
                sda.Fill(__ds);
            }
            catch
            {
                throw;
            }
            return __ds;
        }
        public static DataSet ExecuteDataSet(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            DataSet __ds = new DataSet();
            SqlCommand cmd = new SqlCommand();
            SqlConnection conn = new SqlConnection(connectionString);
            SqlDataAdapter sda = new SqlDataAdapter();
            try
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                sda.SelectCommand = cmd;
                sda.Fill(__ds);
                cmd.Parameters.Clear();
                return __ds;
            }
            catch
            {
                conn.Close();
                throw;
            }
        }
        public static object ExecuteScalar(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();

            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
                object val = cmd.ExecuteScalar();
                cmd.Parameters.Clear();
                return val;
            }
        }

        public static object ExecuteScalar(SqlConnection connection, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
            object val = cmd.ExecuteScalar();
            cmd.Parameters.Clear();
            return val;
        }

        public static void CacheParameters(string cacheKey, params SqlParameter[] commandParameters)
        {
            parmCache[cacheKey] = commandParameters;
        }

        public static SqlParameter[] GetCachedParameters(string cacheKey)
        {
            SqlParameter[] cachedParms = (SqlParameter[])parmCache[cacheKey];
            if (cachedParms == null)
                return null;
            SqlParameter[] clonedParms = new SqlParameter[cachedParms.Length];

            for (int i = 0, j = cachedParms.Length; i < j; i++)
                clonedParms[i] = (SqlParameter)((ICloneable)cachedParms[i]).Clone();
            return clonedParms;
        }

        private static void PrepareCommand(SqlCommand cmd, SqlConnection conn, SqlTransaction trans, CommandType cmdType, 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 = cmdType;
            if (cmdParms != null)
            {
                foreach (SqlParameter parm in cmdParms)
                    cmd.Parameters.Add(parm);
            }
        }


    }
}