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Thread: Cast DataTable to get its Update method?

  1. #1

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    Cast DataTable to get its Update method?

    I came across an article (with code) that described how to extend a BindingSource component to add some useful features.

    https://www.codeguru.com/dotnet/exte...rce-component/

    The code includes the following:

    Code:
    Private Sub _PositionChanged(ByVal sender As Object, ByVal e As EventArgs) _
        Handles Me.PositionChanged
        If IsCurrentDirty Then
            If AutoSave Or MessageBox.Show(_msg, "Confirm Save",
                    MessageBoxButtons.YesNo) = DialogResult.Yes Then
                Try
                    'cast table as ITableUpdate to get the Update method
                    CType(_dataTable, Biz._Interface.ITableUpdate).Update()
                Catch ex As Exception
                    Win.Logger.LogError(_form, ex, _dataTable.TableName & " Update")
                End Try
            Else
                Me.CancelEdit()
                _dataTable.RejectChanges()
            End If
            IsCurrentDirty = False
        End If
    End Sub
    The highlighted statement shows "Type 'Biz._Interface.ITableUpdate' is not defined." in the VS Error List.

    The article was written in 2008 and the author isn't available to answer this question.

    How can I fix this problem? Any advice will be much appreciated!
    Last edited by Mark@SF; Aug 11th, 2022 at 04:09 PM.

  2. #2
    eXtreme Programmer .paul.'s Avatar
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    Re: Cast DataTable to get its Update method?

    Why not just…

    _dataTable.UpDate

    ???

    I’ve never seen anything similar to your code before…

  3. #3
    Super Moderator Shaggy Hiker's Avatar
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    Re: Cast DataTable to get its Update method?

    What is Biz? I've never heard of that. Perhaps somebody else has, but if not, then it sounds like the code you have is based on some third party library that you don't have...and based on what you said, it sounds like it may no longer exist.
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  4. #4
    eXtreme Programmer .paul.'s Avatar
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    Re: Cast DataTable to get its Update method?

    Quote Originally Posted by .paul. View Post
    Why not just…

    _dataTable.UpDate

    ???

    I’ve never seen anything similar to your code before…
    Actually… I apologise, it’d be a DataAdaptor you’d update…

    https://docs.microsoft.com/en-us/dot...h-dataadapters

  5. #5

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    Re: Cast DataTable to get its Update method?

    paul and shaggy -

    I know my question is a weird one because it's about code that I didn't write. But, the example that is in the referenced link is very interesting. It was published on the CodeGuru website (so I'm assuming it was a bonafide working example).

    The gist of the article was to extend the BindingSource component to do several useful things, including auto-saving a "dirty" DataRow. In order to do that, the author appears to have figured out how to "map" the DataAdapter.Update method in a generic way (i.e., without explicitly declaring it in the extended BindingSource.

    The line that causes the error involves the ITableUpdate interface. What is that? I couldn't find anything about it via Google.

    I am hoping that somebody reading this thread might know how to do this...
    Last edited by Mark@SF; Aug 11th, 2022 at 08:00 PM.

  6. #6

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    Re: Cast DataTable to get its Update method?

    The author of the CodeGuru article was David Catherman and per the below link, his extended BindingSource article was part of a four-part project.

    https://www.codeguru.com/visual-basi...s-on-tutorial/

    Unfortunately, I can't find the other parts of the project.

  7. #7
    Super Moderator Shaggy Hiker's Avatar
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    Re: Cast DataTable to get its Update method?

    On the face of it, DataAdapter.Update isn't all that special. You can call GetChanges on the Datatable to returns the set of rows that have changes, but even that isn't all that special. The Status of each Datarow will be Unchanged, Added, Modified, or Deleted. You can iterate through the rows in the datatable and call either INSERT (added), UPDATE (modified), or DELETE (deleted) on each row, as appropriate. The difficulty isn't so much the Update method, it's getting an appropriate SQL Statement for each of those different queries.
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  8. #8
    .NUT jmcilhinney's Avatar
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    Re: Cast DataTable to get its Update method?

    Much, if not all, of that looks like a bad idea, including the part that you're trying to use. A DataTable is supposed to be for data storage. Building the retrieval and/or saving of data into that is a crime against the Single Responsibility Principle. It's getting back to the VB6 way of doing things where the Recordset did everything. .NET tends to use multiple smaller types for specific purposes, rather than one big type that does every job.

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