常用的數據訪問底層類

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

/*
 * 所屬層次：數據訪問類組件(數據操作)
 */
namespace DBUtility
{
    /// <summary>
    /// SqlHelper類用於操作數據庫(可升級，擴展) 抽象類+靜態方法。
    /// </summary>
    public abstract class SqlHelper
    {

        //數據庫連接字符串
        //連接字符串在界面層的...的配置文件中。
        //public static readonly string ConnectionStringSqlServer = ConfigurationManager.ConnectionStrings["connectionString"].ConnectionString;
      

        /// <summary>
        ///  給定連接的數據庫用假設參數執行一個sql命令（不返回數據集）
        /// </summary>
        /// <param name="connectionString">一個有效的連接字符串</param>
        /// <param name="commandType">命令類型(存儲過程, 文本, 等等)</param>
        /// <param name="commandText">存儲過程名稱或者sql命令語句</param>
        /// <param name="commandParameters">執行命令所用參數的集合</param>
        /// <returns>執行命令所影響的行數</returns>
        public static int ExecuteNonQuery( CommandType cmdType, string cmdText, SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();

            using (SqlConnection conn = new SqlConnection(connectionString))
            {
                if (conn.State != ConnectionState.Open)
                    conn.Open();

                cmd.Connection = conn;
                cmd.CommandText = cmdText;
                cmd.CommandType = cmdType;

                if (cmd.Parameters != null)
                {
                    cmd.Parameters.Clear();
                }
                if (commandParameters != null)
                {
                    foreach (SqlParameter parm in commandParameters)
                        cmd.Parameters.Add(parm);
                }

                try
                {
                    int val = cmd.ExecuteNonQuery();
                    cmd.Parameters.Clear();
                    return val;
                }
                catch
                {
                    //關閉連接，拋出異常
                    conn.Close();
                    throw;
                }
                finally
                {
                    conn.Close();
                }
            }
        }

        /// <summary>
        /// 執行存儲過程，返回一個輸出參數
        /// </summary>
        /// <param name="connectionString">一個有效的連接字符串</param>
        /// <param name="cmdText">存儲過程名稱</param>
        /// <param name="commandParameters">執行命令所用參數的集合</param>
        /// <returns>輸出參數</returns>
        public static object ExecuteProcGetOutput( string cmdText, string outputParaName, SqlParameter[] commandParameters)
        {
            SqlCommand cmd = new SqlCommand();

            using (SqlConnection conn = new SqlConnection(connectionString))
            {
                if (conn.State != ConnectionState.Open)
                    conn.Open();

                cmd.Connection = conn;
                cmd.CommandText = cmdText;
                cmd.CommandType = CommandType.StoredProcedure;

                if (commandParameters != null)
                {
                    foreach (SqlParameter parm in commandParameters)
                        cmd.Parameters.Add(parm);
                }

                try
                {
                    cmd.ExecuteNonQuery();
                    object val = cmd.Parameters[outputParaName].Value;
                    cmd.Parameters.Clear();
                    return val;
                }
                catch
                {
                    //關閉連接，拋出異常
                    conn.Close();
                    throw;
                }
            }
        }

        /// <summary>
        /// 用執行的數據庫連接執行一個返回數據集的sql命令
        /// </summary>
        /// <param name="connectionString">一個有效的連接字符串</param>
        /// <param name="commandType">命令類型(存儲過程, 文本, 等等)</param>
        /// <param name="commandText">存儲過程名稱或者sql命令語句</param>
        /// <param name="commandParameters">執行命令所用參數的集合</param>
        /// <returns>包含結果的讀取器</returns>
        public static SqlDataReader ExecuteReader( CommandType cmdType, string cmdText, SqlParameter[] commandParameters)
        {
            //創建一個SqlCommand對象
            SqlCommand cmd = new SqlCommand();
            //創建一個SqlConnection對象
            SqlConnection conn = new SqlConnection(connectionString);
            //不能使用using 因爲要返回SqlDataReader,否則外面的SqlDataReader不能使用。

            if (conn.State != ConnectionState.Open)
                conn.Open();

            cmd.Connection = conn;
            cmd.CommandText = cmdText;
            cmd.CommandType = cmdType;

            if (commandParameters != null)
            {
                foreach (SqlParameter parm in commandParameters)
                    cmd.Parameters.Add(parm);
            }
            try
            {
                //調用 SqlCommand  的 ExecuteReader 方法
                SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                //清除參數
                cmd.Parameters.Clear();
                return reader;
            }
            catch
            {
                conn.Close();
                throw;
            }

        }
   
       
        /// <summary>
        /// 用執行的數據庫連接執行一個返回一張表命令
        /// </summary>
        /// <param name="connectionString">一個有效的連接字符串</param>
        /// <param name="commandText">存儲過程名稱或者sql命令語句</param>
        /// <param name="commandParameters">執行命令所用參數的集合</param>
        /// <returns>包含結果的讀取器</returns>
        public static DataTable ExectuteDataTable(string cmdText, SqlParameter[] commandParameters)
        {
           
            //創建一個SqlConnection對象
            SqlConnection conn = new SqlConnection(connectionString);
            //創建一個SqlDataAdapter對象
            SqlDataAdapter sda = new SqlDataAdapter(cmdText,conn);

            if (commandParameters != null)
            {
                foreach (SqlParameter parm in commandParameters)
                    sda.SelectCommand.Parameters.Add(parm);
            }
            try
            {
                //調用 SqlCommand  的 ExecuteReader 方法
                DataTable dt = new DataTable();
                sda.Fill(dt);
                //清除參數
                sda.SelectCommand.Parameters.Clear();
                return dt;
            }
            catch
            {
                conn.Close();
                throw;
            }

        }
   
    }
}