"Geoff" <nodamnspam@email.com> wrote in message
news:95idnXKcZpocJnDenZ2dnUVZ8qednZ2d@pipex.net...
> Hi
>
> Can anybody explain to me what I'm doing wrong or misunderstood in the
> following:
>
> I have two tables, for example, customers and orders. I have loaded these
> into a dataset. I have also created a relation between these two tables
> using the Relation keyword e.g.
>
> ds.Relationships.Add("Customers_Orders", _
> ds.Tables("Customers").Columns("CustomerID"), _
> ds.Tables("Orders").Columns("CustomerID"), True)
>
> I populate both tables with data.
>
> Everything works ok. However, when I choose a row from the Customers
> tables and try to delete it as follows:
>
> Try
>    row.Delete() ' where row has child rows in the Orders table
> Catch ex Exception
>    MessageBox(ex.Message)
> End Try
>
> The thing is that no exception is thrown!!! I was expecting one to be
> thrown. Have I missed something obvious?

>
> Thanks for any help in advance
>
> Geoff
>

"Bart Mermuys" <bmermuys.nospam@hotmail.com> wrote in message
news:OU6cqXwLGHA.532@TK2MSFTNGP15.phx.gbl...
> Hi,
>
> "Geoff" <nodamnspam@email.com> wrote in message
> news:95idnXKcZpocJnDenZ2dnUVZ8qednZ2d@pipex.net...
>> Hi
>>
>> Can anybody explain to me what I'm doing wrong or misunderstood in the
>> following:
>>
>> I have two tables, for example, customers and orders. I have loaded these
>> into a dataset. I have also created a relation between these two tables
>> using the Relation keyword e.g.
>>
>> ds.Relationships.Add("Customers_Orders", _
>> ds.Tables("Customers").Columns("CustomerID"), _
>> ds.Tables("Orders").Columns("CustomerID"), True)
>>
>> I populate both tables with data.
>>
>> Everything works ok. However, when I choose a row from the Customers
>> tables and try to delete it as follows:
>>
>> Try
>>    row.Delete() ' where row has child rows in the Orders table
>> Catch ex Exception
>>    MessageBox(ex.Message)
>> End Try
>>
>> The thing is that no exception is thrown!!! I was expecting one to be
>> thrown. Have I missed something obvious?
>
> When you add a DataRelation, then there's also a ForeignKeyConstraint
> added to the child table.  The ForeignKeyConstraint has a property
> 'DeleteRule'. By default that property is set to Rule.Cascade.  So when
> you delete a parent row, child rows are deleted too and therefore there is
> no reason for an Exception.
>
> You can change this behaviour, eg. :
>
> ds.Relations("Customers_Orders").ChildKeyConstraint.DeleteRule = Rule.None
>
> If you delete a parent row now and the parent has child rows, it will
> throw an exception, because the child rows would become orphaned.
>
>
> HTH,
> Greetings
>
>
>>
>> Thanks for any help in advance
>>
>> Geoff
>>
>
>