并发冲突问题

Question

T_MemTypeAdvanceBooking表中有这些列：

CentreID    Int    PrimaryKey 
MembershipType   Uniqueindentifier PrimaryKey 
FacilityName   UniqueIdentifier PrimaryKey 
ActivityName   NvarChar(35)  PrimaryKey 
NumOfAdvanceDaysBooking smallint 

我知道可能会为拥有这些主键听起来很傻，但在我的应用程序时，我填写的所有按键和我做一个插入，它没问题！但是当我尝试用NumOfAdvancedDaysBooking的不同的值更新行，它抛出ConcurrencyViolation之外，怎么是这样的？对我来说这是什么修复？ 这里ISTE更新命令：

Me.SqlUpdateCommand1.CommandText = "UPDATE [T_MemTypeAdvanceBooking] SET [CentreId" & _ 
    "] = @CentreId, [MembershipTypeId] = @MembershipTypeId, [MAIN FACILITY USED] = @M" & _ 
    "AIN_FACILITY_USED, [ActivityType] = @ActivityType, [NumOfAdvanceDays] = @NumOfAd" & _ 
    "vanceDays WHERE (([CentreId] = @Original_CentreId) AND ([MembershipTypeId] = @Or" & _ 
    "iginal_MembershipTypeId) AND" & _ 
    "([ActivityType] = @Original_ActivityType) AND ([RowVer] = @Original_RowVe" & _ 
    "r));" 

Answer 1

删除RowVer条件：

Me.SqlUpdateCommand1.CommandText = "UPDATE [T_MemTypeAdvanceBooking] SET [CentreId" & _ 
    "] = @CentreId, [MembershipTypeId] = @MembershipTypeId, [MAIN FACILITY USED] = @M" & _ 
    "AIN_FACILITY_USED, [ActivityType] = @ActivityType, [NumOfAdvanceDays] = @NumOfAd" & _ 
    "vanceDays WHERE (([CentreId] = @Original_CentreId) AND ([MembershipTypeId] = @Or" & _ 
    "iginal_MembershipTypeId) AND" & _ 
    "([ActivityType] = @Original_ActivityType));" 

说明：

当您在数据表更新的DataRow你实际上得到2行。一个与DataRowVersion当前和另一个与原始。大多数时候您使用当前版本的DataRow。因此，当您发送更新的行时（通常通过DataAdapter）RowVersion不等于原始，但当前。接下来会发生的情况是该条件是错误的，并且数据库中没有记录被更新。 DataAdapter获取没有记录更新的信息，并认为某人更新了您之前的记录并引发了并发异常。

我建议你对你的表型整数列版本添加。当插入您设置版本为1。在每一个后续更新您可以通过1递增版本这样你就可以通过只比较牵强版本值（@Original_Version）与实际版本值（[版本]）发行时DB更新检查乐观并发声明。

Me.SqlUpdateCommand1.CommandText = "UPDATE [T_MemTypeAdvanceBooking] SET [CentreId" & _ 
    "] = @CentreId, [MembershipTypeId] = @MembershipTypeId, [MAIN FACILITY USED] = @M" & _ 
    "AIN_FACILITY_USED, [ActivityType] = @ActivityType, [NumOfAdvanceDays] = @NumOfAd" & _ 
    "vanceDays WHERE (([CentreId] = @Original_CentreId) AND ([MembershipTypeId] = @Or" & _ 
    "iginal_MembershipTypeId) AND" & _ 
    "([ActivityType] = @Original_ActivityType) AND ([Version] = @Original_Version));"