Dataset HasChanges function not true when Dataset is passed as variable

26 Jun 2006 6:32 PM

darjonase

I am having a problem, and I wonder if anyone could help me with it. I
have two methods. The first on a form calls the second method which is
located in a class lib.

'Form Method
Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles btnSave.Click
        'If imageDataSet.HasChanges Then
        _databaseMethods.ProcessUpdates(imageDataSet)
        'End If
End Sub

'Class Method
Public Sub ProcessUpdates(ByRef dsData As DataSet)
        Try
            If dsData.HasChanges(DataRowState.Modified) Then
                Dim dsChangedDataSet As DataSet
                dsChangedDataSet =
dsData.GetChanges(DataRowState.Modified)

                If dsChangedDataSet.HasChanges Then
                    HandleDataSetErrors(dsChangedDataSet)
                Else
                    UpdateImagesInDB(dsChangedDataSet)
                End If
            End If
        Catch ex As Exception
            MessageBox.Show(ex.ToString)
        End Try
End Sub

When I pass the imageDataSet object to the ProcessUpdates method, the
..HasChanges function will always return a false. If, however, I check
the .HasChanges function on the imageDataSet object before it is
passed, it will return a true value.

Ideas on this one?
Darian Bonnell

26 Jun 2006 6:53 PM

Cor Ligthert [MVP]

Darjonase,

Can you try passing it ByValue.
Byval is a little bit more efficient in this procedure while it is the
normal way as this is done.

Cor

<darjon***@gmail.com> schreef in bericht
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news:1151346727.428542.66710@m73g2000cwd.googlegroups.com...
>I am having a problem, and I wonder if anyone could help me with it. I
> have two methods. The first on a form calls the second method which is
> located in a class lib.
>
> 'Form Method
> Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles btnSave.Click
>        'If imageDataSet.HasChanges Then
>        _databaseMethods.ProcessUpdates(imageDataSet)
>        'End If
> End Sub
>
> 'Class Method
> Public Sub ProcessUpdates(ByRef dsData As DataSet)
>        Try
>            If dsData.HasChanges(DataRowState.Modified) Then
>                Dim dsChangedDataSet As DataSet
>                dsChangedDataSet =
> dsData.GetChanges(DataRowState.Modified)
>
>                If dsChangedDataSet.HasChanges Then
>                    HandleDataSetErrors(dsChangedDataSet)
>                Else
>                    UpdateImagesInDB(dsChangedDataSet)
>                End If
>            End If
>        Catch ex As Exception
>            MessageBox.Show(ex.ToString)
>        End Try
> End Sub
>
> When I pass the imageDataSet object to the ProcessUpdates method, the
> .HasChanges function will always return a false. If, however, I check
> the .HasChanges function on the imageDataSet object before it is
> passed, it will return a true value.
>
> Ideas on this one?
> Darian Bonnell
>

26 Jun 2006 7:18 PM

darjonase

That didn't seem to do anything. Also, this may help find an answer.
When I put the .HasChanges in the form method it is set to True as I
said before. When I then call the method in the class lib, the
..GetChanges method does not return anything at all.

Thanks for any help all,
Darian

26 Jun 2006 8:11 PM

Terry

I am not an expert on this subject, but haveing just read an article on this
subject .... Are you positive that changing it to 'ByVal' had no effect? You
need to be carefull when passing object references. ByVal does NOT create a
copy of the object, but a copy of the reference! ie a new pointer to the
DataSet object. Whereas, ByRef will pass a reference to the original
'reference'. So ByRef would allow you to change the original pointer to
'Nothing' for example. As best as I can understand it the ByRef argument is
an 'indirect' reference to the orgingal Object (DataSet in this example).
Again, I am not an expert and would like to hear from them on this subject.

--
Terry

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"darjon***@gmail.com" wrote:

> That didn't seem to do anything. Also, this may help find an answer.
> When I put the .HasChanges in the form method it is set to True as I
> said before. When I then call the method in the class lib, the
> ..GetChanges method does not return anything at all.
>
> Thanks for any help all,
> Darian
>
>

26 Jun 2006 9:27 PM

Terry

Just looking at your code again... Don't you have to call 'AcceptChanges'
before you can call GetChanges? Also, in the calling routine, you are
looking at all changes and in the called routine you are filtering to only
changes of type 'Modified' so it is possible to true in the calling routine
and not true in the called routine.

--
Terry

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"darjon***@gmail.com" wrote:

> That didn't seem to do anything. Also, this may help find an answer.
> When I put the .HasChanges in the form method it is set to True as I
> said before. When I then call the method in the class lib, the
> ..GetChanges method does not return anything at all.
>
> Thanks for any help all,
> Darian
>
>

27 Jun 2006 6:47 AM

M. Posseth

Hi Terry

i believe you are right

dataset.getchanges()

Gets a copy of the DataSet that contains all changes made to it since it was
loaded or since AcceptChanges was last called.

or

dataset.getchanges(datarowstate)

Gets a copy of the DataSet containing all changes made to it since it was
last loaded, or since AcceptChanges was called, filtered by DataRowState.

regards

Michel Posseth [MCP]

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"Terry" wrote:

> Just looking at your code again... Don't you have to call 'AcceptChanges'
> before you can call GetChanges? Also, in the calling routine, you are
> looking at all changes and in the called routine you are filtering to only
> changes of type 'Modified' so it is possible to true in the calling routine
> and not true in the called routine.
> --
> Terry
>
>
> "darjon***@gmail.com" wrote:
>
> > That didn't seem to do anything. Also, this may help find an answer.
> > When I put the .HasChanges in the form method it is set to True as I
> > said before. When I then call the method in the class lib, the
> > ..GetChanges method does not return anything at all.
> >
> > Thanks for any help all,
> > Darian
> >
> >

26 Jun 2006 9:50 PM

Terry

Ok, forget the statement about AcceptChanges ... My Bad!

--
Terry

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"darjon***@gmail.com" wrote:

> That didn't seem to do anything. Also, this may help find an answer.
> When I put the .HasChanges in the form method it is set to True as I
> said before. When I then call the method in the class lib, the
> ..GetChanges method does not return anything at all.
>
> Thanks for any help all,
> Darian
>
>

27 Jun 2006 6:48 AM

Cor Ligthert [MVP]

Darian,

Why have you commented out that If haschanges text in your code, are you
sure you are talking about the same?

Cor

<darjon***@gmail.com> schreef in bericht
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news:1151349501.370760.134280@u72g2000cwu.googlegroups.com...
> That didn't seem to do anything. Also, this may help find an answer.
> When I put the .HasChanges in the form method it is set to True as I
> said before. When I then call the method in the class lib, the
> .GetChanges method does not return anything at all.
>
> Thanks for any help all,
> Darian
>