整理出一个比较实用的SqlHelper类 满足大多数情况的使用

　　 /// <summary>
    /// SqlHelper类 by zy 2017-8-17
    /// </summary>
    public sealed class SqlHelper
    {
        //如果项目中只连接了一个数据库 那么可以在此定义一个固定的连接字符串
        private static string connectionStr = ConfigurationManager.ConnectionStrings["SQLConnString1"].ConnectionString;

        #region ExecuteNonQuery

        /// <summary>
        /// 执行sql语句 返回受影响行数
        /// </summary>
        /// <param name="connectionString">连接字符串</param>
        /// <param name="cmdType">command类型</param>
        /// <param name="cmdText">sql语句</param>
        /// <param name="commandParameters">参数</param>
        /// <returns></returns>
        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;
            }
        }

        /// <summary>
        /// 执行sql语句 返回当前插入的记录id(其实是ExecuteScalar转换成id返回)
        /// </summary>
        /// <param name="connectionString">连接字符串</param>
        /// <param name="cmdType">command类型</param>
        /// <param name="cmdText">sql语句</param>
        /// <param name="returnID">返回id</param>
        /// <param name="commandParameters">参数</param>
        /// <returns></returns>
        public static int ExecuteNonQuery(string connectionString, CommandType cmdType, string cmdText, out int returnID, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();

            using (SqlConnection conn = new SqlConnection(connectionString))
            {
                returnID = 0;
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                returnID = (Int32)cmd.ExecuteScalar();
                cmd.Parameters.Clear();
                return returnID;
            }
        }

        /// <summary>
        /// 执行sql语句 返回受影响行数(数据库连接SqlConnection)
        /// </summary>
        /// <param name="connection">SqlConnection连接</param>
        /// <param name="cmdType">command类型</param>
        /// <param name="cmdText">sql语句</param>
        /// <param name="commandParameters">参数</param>
        /// <returns></returns>
        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;
        }

        /// <summary>
        /// 执行sql语句 返回受影响行数(事务SqlTransaction)
        /// </summary>
        /// <param name="trans">SqlTransaction事务</param>
        /// <param name="cmdType">command类型</param>
        /// <param name="cmdText">sql语句</param>
        /// <param name="commandParameters">参数</param>
        /// <returns></returns>
        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;
        }

        #endregion

        #region ExecuteScalar

        /// <summary>
        /// 执行sql语句 返回结果集第一行第一列
        /// </summary>
        /// <param name="connectionString">连接字符串</param>
        /// <param name="cmdType">Command类型</param>
        /// <param name="cmdText">sql语句</param>
        /// <param name="commandParameters">参数</param>
        /// <returns></returns>
        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;
            }
        }
        /// <summary>
        /// 执行sql语句 返回结果集第一行第一列(事务)
        /// </summary>
        /// <param name="trans">SqlTransaction事务</param>
        /// <param name="cmdType">Command类型</param>
        /// <param name="cmdText">sql语句</param>
        /// <param name="commandParameters">参数</param>
        /// <returns></returns>
        public static object ExecuteScalar(SqlTransaction trans, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, trans.Connection, trans, cmdType, cmdText, commandParameters);
            object val = cmd.ExecuteScalar();
            cmd.Parameters.Clear();
            return val;
        }

        /// <summary>
        /// 执行sql语句 返回结果集第一行第一列(数据库连接)
        /// </summary>
        /// <param name="connection">SqlConnection连接</param>
        /// <param name="cmdType">Command类型</param>
        /// <param name="cmdText">sql语句</param>
        /// <param name="commandParameters">参数</param>
        /// <returns></returns>
        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;
        }

        #endregion

        #region ExecuteReader

        /// <summary>
        /// 执行sql语句 返回reader
        /// </summary>
        /// <param name="connectionString">连接字符串</param>
        /// <param name="cmdType">command类型</param>
        /// <param name="cmdText">sql语句</param>
        /// <param name="commandParameters">参数</param>
        /// <returns></returns>
        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;
            }
        }

        #endregion

        #region DataSet

        /// <summary>
        /// 执行sql语句 返回DataSet结果集(无参数)
        /// </summary>
        /// <param name="connectionString">连接字符串</param>
        /// <param name="commandType">command类型</param>
        /// <param name="commandText">sql语句</param>
        /// <returns></returns>
        public static DataSet ExecuteDataset(string connectionString, CommandType commandType, string commandText)
        {
            return ExecuteDataset(connectionString, commandType, commandText, (SqlParameter[])null);
        }

        /// <summary>
        /// 执行sql语句 返回DataSet结果集
        /// </summary>
        /// <param name="connectionString">连接字符串</param>
        /// <param name="commandType">command类型</param>
        /// <param name="commandText">sql语句</param>
        /// <param name="commandParameters">参数</param>
        /// <returns></returns>
        public static DataSet ExecuteDataset(string connectionString, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //创建数据库连接 完成后dispose
            using (SqlConnection cn = new SqlConnection(connectionString))
            {
                cn.Open();

                //根据数据库连接 调用具体方法
                return ExecuteDataset(cn, commandType, commandText, commandParameters);
            }
        }

        /// <summary>
        /// 执行sql语句 返回DataSet结果集(数据库连接SqlConnection)
        /// </summary>
        /// <param name="connection">SqlConnection连接</param>
        /// <param name="commandType">command类型</param>
        /// <param name="commandText">sql语句</param>
        /// <param name="commandParameters">参数</param>
        /// <returns></returns>
        public static DataSet ExecuteDataset(SqlConnection connection, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            //创建command
            SqlCommand cmd = new SqlCommand();
            //准备command对象
            PrepareCommand(cmd, connection, (SqlTransaction)null, commandType, commandText, commandParameters);

            //创建SqlDataAdapter和DataSet
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataSet ds = new DataSet();

            //把结果集装进dataset
            da.Fill(ds);

            //返回
            return ds;
        }

        #endregion DataSet

        #region DataTable

        /// <summary>
        /// 执行sql语句 返回DataTable结果集(无参数)
        /// </summary>
        /// <param name="connectionString">连接字符串</param>
        /// <param name="commandType">command类型</param>
        /// <param name="commandText">sql语句</param>
        /// <returns></returns>
        public static DataTable ExecuteDataTable(string connectionString, CommandType commandType, string commandText)
        {
            return ExecuteDataTable(connectionString, commandType, commandText, (SqlParameter[])null);
        }

        /// <summary>
        /// 执行sql语句 返回DataTable结果集
        /// </summary>
        /// <param name="connectionString">连接字符串</param>
        /// <param name="commandType">command类型</param>
        /// <param name="commandText">sql语句</param>
        /// <param name="commandParameters">参数</param>
        /// <returns></returns>
        public static DataTable ExecuteDataTable(string connectionString, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            using (SqlConnection cn = new SqlConnection(connectionString))
            {
                cn.Open();
                return ExecuteDataTable(cn, commandType, commandText, commandParameters);
            }
        }

        /// <summary>
        /// 执行sql语句 返回DataTable结果集
        /// </summary>
        /// <param name="connection">SqlConnection连接</param>
        /// <param name="commandType">command类型</param>
        /// <param name="commandText">sql语句</param>
        /// <param name="commandParameters">参数</param>
        /// <returns></returns>
        public static DataTable ExecuteDataTable(SqlConnection connection, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();
            PrepareCommand(cmd, connection, (SqlTransaction)null, commandType, commandText, commandParameters);

            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();

            da.Fill(dt);

            return dt;
        }

        #endregion DataTable

        #region PrepareCommand

        /// <summary>
        /// 准备Command对象
        /// </summary>
        /// <param name="cmd">SqlCommand 对象</param>
        /// <param name="conn">SqlConnection 对象</param>
        /// <param name="trans">SqlTransaction 对象</param>
        /// <param name="cmdType">Command 类型</param>
        /// <param name="cmdText">sql语句</param>
        /// <param name="cmdParms">参数</param>
        private static void PrepareCommand(SqlCommand cmd, SqlConnection conn, SqlTransaction trans, CommandType cmdType, string cmdText, SqlParameter[] cmdParms)
        {
            //打开SqlConnection连接
            if (conn.State != ConnectionState.Open)
                conn.Open();
            //给Command的Connection CommandText设置值
            cmd.Connection = conn;
            cmd.CommandText = cmdText;
            //如果是事务 设置事务
            if (trans != null)
                cmd.Transaction = trans;
            //Command类型
            cmd.CommandType = cmdType;
            //Command参数
            if (cmdParms != null)
            {
                foreach (SqlParameter parm in cmdParms)
                {
                    //在此可以操作参数 比如把参数值里的英文逗号全部改为中文逗号 或者其他操作
                    //switch (parm.SqlDbType)
                    //{
                    //    case SqlDbType.Char:
                    //    case SqlDbType.NChar:
                    //    case SqlDbType.NText:
                    //    case SqlDbType.NVarChar:
                    //    case SqlDbType.Text:
                    //    case SqlDbType.VarChar:
                    //        if (parm.Value != null && parm.Value != DBNull.Value && parm.ParameterName != "@SQLClause")
                    //        {
                    //            string tmp = parm.Value.ToString();
                    //            tmp = tmp.Replace(",", "，");
                    //            tmp = tmp.Replace("‘", "＇");
                    //            parm.Value = tmp;
                    //        }
                    //        break;
                    //}


                    //把参数添加到Command中的Parameters中
                    cmd.Parameters.Add(parm);
                }
            }
        }

        #endregion
    }