/// <summary>
/// 事物
/// </summary>
/// <param name="dbName"></param>
public static void BeginTransaction(string dbName)
{
CheckDbName(dbName);
string key = GetKey(dbName);
if (ServiceContext.Current.Contains(key))
{
throw new InvalidOperationException(string.Format("数据库{0}的上下文环境已经存在。", dbName));
}
DataAccessContext dac = new DataAccessContext(GetDatabase(dbName));
ServiceContext.Current.Add(key, dac);
dac.BeginTransaction();
}