基于TransactionScope類的分布式隱式事務

System.Transactions 命名空間中除了上一節中提到的基于 Transaction 類的顯式編程模型，還提供使用 TransactionScope 類的隱式編程模型，它與顯示編程模型相比，更加方便簡單，它也是MSDN中建議使用的編程模型。

下面，我們基于TransactionScope類實現上一節銀行轉帳的例程。

示例代碼：

（1）SqlHelper.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Configuration;

using MySQL.Data.MySqlClient;

using System.Transactions;

using System.Data;

namespace 事務處理

{

    public class SqlHelper

    {

        public static string GetConnection()

        {

            string connStr = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;

            return connStr;

        }

        public static int ExecuteNonQuery(string sql, params MySqlParameter[] parameters)

        {

            int result = -1;

            using (MySqlConnection conn = new MySqlConnection(GetConnection()))

            {

                conn.Open();

                using (MySqlCommand cmd = conn.CreateCommand())

                {

                    cmd.CommandText = sql;

                    cmd.Parameters.AddRange(parameters);

                    result = cmd.ExecuteNonQuery();

                }

            }

            return result;

        }

        public static DataTable ExecuteDataTable(string sql, params MySqlParameter[] parameters)

        {

            using (MySqlConnection conn = new MySqlConnection(GetConnection()))

            {

                using (MySqlCommand cmd = conn.CreateCommand())

                {

                    cmd.CommandText = sql;

                    cmd.Parameters.AddRange(parameters);

                    using (MySqlDataAdapter da = new MySqlDataAdapter(cmd))

                    {

                        using (DataSet ds = new DataSet())

                        {

                            da.Fill(ds);

                            return ds.Tables[0];

                        }

                    }

                }

            }

        }

    }

}

（2）Bankaccountn.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using MySql.Data.MySqlClient;

using System.Data;

using System.Transactions;

namespace 事務處理

{

    public class Bankaccountn

    {

        public Bankaccountn(string bankaccountnId)

        {

            string sql = @"SELECT * FROM Bankaccountn WHERE BankaccountnId=@BankaccountnId;";

            DataTable dt = SqlHelper.ExecuteDataTable(sql, new MySqlParameter("@BankaccountnId", bankaccountnId));

            if (dt.Rows.Count <= 0)

            {

                throw new Exception("賬戶不存在！");

            }

            else if (dt.Rows.Count > 1)

            {

                throw new Exception("異常信息：有重名的賬戶存在！");

            }

            else

            {

                this.bankaccountnId = dt.Rows[0]["BankaccountnId"] as string;

                this.UserName = dt.Rows[0]["UserName"] as string;

                this.Balance = Convert.ToDecimal(dt.Rows[0]["Balance"]);

            } 

        }

        PRivate string bankaccountnId;

        public string UserName

        { 

            get; 

            private set; 

        }

        public decimal Balance

        {

            get;

            private set;

        }

        protected int Update()

        {

            string sql = @"UPDATE bankaccountn SET UserName = @UserName,Balance = @Balance 

                           WHERE BankaccountnId= @BankaccountnId;";

            return SqlHelper.ExecuteNonQuery(sql, new MySqlParameter("@BankaccountnId", this.bankaccountnId), new MySqlParameter("@UserName", this.UserName), new MySqlParameter("@Balance", this.Balance));

        }

        public void Epend( decimal money)

        {

            this.Balance -= money;

            this.Update();

        }

        public void Income(decimal money)

        {

            this.Balance += money;

            this.Update();

        }

        public bool HiddenTransferOfAccount(string incomeBankaccountnId, decimal money)

        {

            bool result = true;

            using (TransactionScope scope = new TransactionScope())

            {

                try

                {

                    Bankaccountn incomeBankaccountn = new Bankaccountn(incomeBankaccountnId);

                    incomeBankaccountn.Income(money); //收款賬戶入賬

                    this.Epend(money); //付款賬戶支出

                    scope.Complete();

                }

                catch (Exception ex)

                {

                    //這里寫做異常信息的記錄的代碼

                    result = false;

                }

            }

            return result;

        }

    }

}

（3）測試代碼

Bankaccountn one = new Bankaccountn("6666660123456789");

if (one.HiddenTransferOfAccount("6666669876543210", 200M))

{

    Response.Write("<scr
}
else
{
    Response.Write("<script>alert('轉賬失敗')</script>");
}
代碼分析：
使用TransactionScope 之后，事務管理器會 預執行代碼，直至Complete()處，如果過程沒有出錯，這通知事務管理器去提交，如果錯誤就不提交，保證了整個執行過程的一致性。
但，在使用隱式編程模型時應注意以下幾點：
1）要確保參與事務的資源（如連接的打開等）的全登記放在TransactionScope 實例化對象之后，調用Complete()方法之前。
2）從TransactionScope 實例化到調用Complete()方法之間的代碼，不要吃掉異常。
using (TransactionScope scope = new TransactionScope())
{
    try
    {
        //要確保參與事務的資源全部登記在這個位置（如連接的打開等）
         Bankaccountn incomeBankaccountn = new Bankaccountn(incomeBankaccountnId);
         incomeBankaccountn.Income(money); //收款賬戶入賬
         this.Epend(money); //付款賬戶支出
         scope.Complete();
    }
    catch (Exception ex)
    {
         //捕獲異常要在這個位置
          result = false;
    }
}