IsNotAllowDBNullViolated方法在调用DataSet.Clear期间抛出NullReferenceException [英] IsNotAllowDBNullViolated method throws NullReferenceException during call to DataSet.Clear

问题描述

这是另一个奇怪的。我有一个带有两个表的DataSet：

OrderHeaders（主键是[OrderID]）

• OrderID - Int32


• OrderName - String

OrderDetails（主键是[OrderID，DetailID]）

• OrderID - Int32（与OrderHeaders表的'OrderID'列相关联）


• DetailID - Int32


• ItemName - String

OrderDetails表绑定到我的Windows应用程序中的DataGridView。 "OrderID"列是DataGridViewComboBoxColumn。我可以毫无问题地加载和显示网格中的数据。我甚至可以毫无问题地插入和删除行。坚持对数据库的更改可以完美地运行。但是，当我尝试使用新值刷新DataSet时，我一直遇到问题。当我调用DataSet的'Clear（）'方法时，System.Data.DataColumn.IsNotAllowDBNullViolated（）方法抛出NullReferenceException。例如，如果我的DataSet名为'dsOrders'，并且我调用'dsOrders.Clear（）'以从DataSet中删除所有数据，则会抛出异常！如果我首先设置'dsOrders.EnforceConstraints = False'，然后调用'dsOrders.Clear（）'，然后重新强制执行约束，则在调用期间抛出异常以重新强制执行约束。我相信这必须是System.Data.DataColumn类的'IsNotAllowDBNullViolated（）'方法中的错误。任何人都可以为我阐明这一点吗？

另一个注意事项：我在开发一个在DataSet中有两个以上DataTables的真实应用程序时遇到了这个bug。我试图在一个非常简化的测试应用程序中重现此错误。在测试应用程序中，当我调用DataSet的'Clear（）'方法时抛出异常，但是如果我调用各个表的'Clear（）'方法，则不会抛出异常。在实际应用程序中，无论是否在DataSet或各个表上调用"Clear（）"，都会抛出异常。在这两种情况下，我都确信我按照正确的顺序在表上调用'Clear（）'方法（根据DataSet中的约束）。

解决方案

你好，

我有类似的问题（尽管我没有在我的数据库和数据集中使用参照完整性contstaints）。

如果我将数据集。 EnforceConstraints属性设置为false，问题就解决了。

问候，mnb

Here's another weird one.  I have a DataSet with two tables:

OrderHeaders (primary key is [OrderID])

• OrderID - Int32
• OrderName - String

OrderDetails (primary key is [OrderID, DetailID])

• OrderID - Int32 (tied to the OrderHeaders table's 'OrderID' column)
• DetailID - Int32
• ItemName - String

The OrderDetails table is bound to a DataGridView in my windows application.  The column for 'OrderID' is a DataGridViewComboBoxColumn.  I can load and display the data in the grid without any problems.  I can even insert and delete rows without a problem.  Persisting the changes to the database works flawlessly.  However, I keep encountering a problem when I try to refresh the DataSet with new values.  A NullReferenceException is being thrown by the System.Data.DataColumn.IsNotAllowDBNullViolated() method when I call the 'Clear()' method of my DataSet.  For example, if my DataSet is named 'dsOrders', and I make a call to 'dsOrders.Clear()' to remove all data from the DataSet, an exception is thrown!  If I first set 'dsOrders.EnforceConstraints = False', then call 'dsOrders.Clear()', and then re-enforce constraints, the exception is thrown during the call to re-enforce the constraints.  I believe this must be a bug in the 'IsNotAllowDBNullViolated()' method of the System.Data.DataColumn class.  Can anyone shed any light on this for me?

One other note:  I encountered this bug during development of a real-world application that had more than two DataTables in the DataSet.  I attempted to reproduce this bug in a very simplified test app.  In the test app, the exception is thrown when I make a call to the 'Clear()' method of the DataSet, but the exception is NOT thrown if I make a call to the 'Clear()' methods of the individual tables.  In the real-world application, the exception is thrown regardless of whether I make the call to 'Clear()' on the DataSet or the individual tables.  In both cases, I have assured that I call the 'Clear()' method on the tables in the proper order (according to constraints within the DataSet).

解决方案

 

Hello,

 

I have a similar problem (altough I did not use referential integrity contstaints in my database and dataset).

If I set the dataset.EnforceConstraints property to false, the problem was solved.

Regards, mnb

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