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

namespace Lhtdco.SZOnline.DBUtility
{    
    /// <summary>
    /// 數(shù)據(jù)庫操作類
    /// </summary>
    public abstract class SqlHelper
    {
        
        // 數(shù)據(jù)庫連接字符串
        public static readonly string ConnectionString = String.Empty ;// ConfigurationManager.ConnectionStrings["SQLConnString"].ConnectionString;
        //public static readonly string ConnectionString = "Server=XHL;database=Center2006;uid=sa;pwd=lhtdco";

        // 存儲(chǔ)緩存參數(shù)的 HashTable
        private static Hashtable parmCache = Hashtable.Synchronized(new Hashtable());

        // 因?yàn)榇祟愄峁┑亩际庆o態(tài)方法,為了防止此類被以"new SqlHelper()"方式構(gòu)造,我們將此類的默認(rèn)構(gòu)造函數(shù)私有化.
        private SqlHelper() { }

        #region  === ExecuteNonQuery === 

        /// <summary>
        /// 執(zhí)行命令并返回影響的記錄數(shù).
        /// </summary>
        /// <param name="connectionString">一個(gè)有效的數(shù)據(jù)庫連接串</param>
        /// <param name="commandType">命令類型</param>
        /// <param name="commandText">T-SQL語句或存儲(chǔ)過程名</param>
        /// <param name="commandParameters">SqlParamters 集合</param>
        /// <returns>受影響的記錄條數(shù)</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>
        /// 執(zhí)行命令并返回影響的記錄數(shù).
        /// </summary>
        /// <param name="conn">一個(gè)有效的數(shù)據(jù)庫連接</param>
        /// <param name="commandType">命令類型</param>
        /// <param name="commandText">T-SQL語句或存儲(chǔ)過程名</param>
        /// <param name="commandParameters">SqlParamters 集合</param>
        /// <returns>受影響的記錄條數(shù)</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>
        /// 執(zhí)行命令并返回影響的記錄數(shù).
        /// </summary>
        /// <param name="trans">一個(gè)存在的事務(wù)</param>
        /// <param name="commandType">命令類型</param>
        /// <param name="commandText">T-SQL語句或存儲(chǔ)過程名</param>
        /// <param name="commandParameters">SqlParamters 集合</param>
        /// <returns>受影響的記錄條數(shù)</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 === ExecuteReader === 

        /// <summary>
        /// Execute a SqlCommand that returns a resultset against the database specified in the connection string 
        /// using the provided parameters.
        /// </summary>
        /// <param name="connectionString">a valid connection string for a SqlConnection</param>
        /// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
        /// <param name="commandText">the stored procedure name or T-SQL command</param>
        /// <param name="commandParameters">an array of SqlParamters used to execute the command</param>
        /// <returns>A SqlDataReader containing the results</returns>
        public static SqlDataReader ExecuteReader(string connectionString, CommandType cmdType, string cmdText, params SqlParameter[] commandParameters) {
            SqlCommand cmd = new SqlCommand();
            SqlConnection conn = new SqlConnection(connectionString);

            // we use a try/catch here because if the method throws an exception we want to 
            // close the connection throw code, because no datareader will exist, hence the 
            // commandBehaviour.CloseConnection will not work
            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 === ExecuteScalar ===

        /// <summary>
        /// 返回查詢結(jié)果中的第一行的第一列
        /// </summary>
        /// <param name="connectionString">一個(gè)有效的數(shù)據(jù)庫連接串</param>
        /// <param name="commandType">命令類型</param>
        /// <param name="commandText">T-SQL語句或存儲(chǔ)過程名</param>
        /// <param name="commandParameters">SqlParamters 集合</param>
        /// <returns>查詢結(jié)果中的第一行的第一列數(shù)據(jù)</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>
        /// 返回查詢結(jié)果中的第一行的第一列
        /// </summary>
        /// <param name="conn">一個(gè)有效的數(shù)據(jù)庫連接</param>
        /// <param name="commandType">命令類型</param>
        /// <param name="commandText">T-SQL語句或存儲(chǔ)過程名</param>
        /// <param name="commandParameters">SqlParamters 集合</param>
        /// <returns>查詢結(jié)果中的第一行的第一列數(shù)據(jù)</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

        /// <summary>
        /// 將參數(shù)數(shù)組添加到緩存中
        /// </summary>
        /// <param name="cacheKey">緩存關(guān)鍵字</param>
        /// <param name="cmdParms">要緩存的參數(shù)數(shù)組</param>
        public static void CacheParameters(string cacheKey, params SqlParameter[] commandParameters) {
            parmCache[cacheKey] = commandParameters;
        }

        /// <summary>
        /// 取回緩存中的相應(yīng)參數(shù)
        /// </summary>
        /// <param name="cacheKey">緩存關(guān)鍵字</param>
        /// <returns>Cached SqlParamters 數(shù)組</returns>
        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;
        }

        /// <summary>
        /// 準(zhǔn)備一條命令信息
        /// </summary>
        /// <param name="cmd">SqlCommand 對(duì)象</param>
        /// <param name="conn">SqlConnection 對(duì)象</param>
        /// <param name="trans">SqlTransaction 對(duì)象</param>
        /// <param name="cmdType">SqlCommand 類型</param>
        /// <param name="cmdText">命令內(nèi)容</param>
        /// <param name="cmdParms">SqlParameters 數(shù)組</param>
        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);
            }
        }
    }
}