How can I choose by program to load from DB or xml-file

[smktec]

I work with MS Access database which works fine. Now, for a presentation I would like to run the .exe file on my tablet which works, too.
Unfortunately, I do not have MS access there and would like to export and import the date using dataset.writexml and dataset.readxml. Even that seems to work as long as the tables have never been set up to load from DB.

Now, I am not sure, how to stop the program from trying to load from the DB and rather load the xml data, instead, or even better, if the program would ask at start where to load from.

Could somebody help, please?

[Sitten Spynne]

It takes some work and thought. What you need is "an abstraction layer".

That means making an abstract type or interface that does all the things you want the DB or the text file to do. Then you make one implementation that uses a text file, and a different implementation that uses the real DB.

Then, in your program, have some switch somewhere (or maybe a special build) that makes it choose the text file version.

(An example would be sort of involved, and someone else might have to write it. I can't think of a way to write it that'd make you happy and not take me a few hours. I don't have Access, I don't use DataAdapters/DataSets, so I'd be fumbling along pretty slowly or writing stuff completely different from what you want to see.)

[smktec]

from what say and thinking a little bit about it, it sounds like the problem are the tableadapters, which communicate conviently with the db. If they could be stopped or replaced by something else which loads the tables, then I could choose where the data should come from. Is this assumption corrrect?

[Sitten Spynne]

More or less, yes.

At a high level, all your app probably cares about is getting a DataSet or some DataTables that you throw at a DataGridView or whatever. So conceptually, all your application needs is something like:

Public Interface IDataFetcher

    Function GetData() As DataSet

End Interface

The code you have right now more or less implements that using the TableAdapters:

Public Class DatabaseDataFetcher
    Implements IDataFetcher

    Public Function GetData() As DataSet Implements IDataFetcher.GetData
        ' Do things with TableAdapters
        Return results
    End Function
End Class

You could also make an implementation that uses files:

Public Class FileDataFetcher
    Implements IDataFetcher

    Public Function GetData() As DataSet Implements IDataFetcher.GetData
        ' Do things with files
        Return results
    End Function
End Class

The way you "stop or replace that" is to make a decision at the point where you load the data. Right now it probably looks like this:

Sub Button384_Click(...) Handles Button2384.Click
    ' Do things with TableAdapters
    DataGridView83.DataSource = results
End Sub

You'd change it to something like this:

Dim dataFetcher As IDataFetcher
If My.Settings.IsUsingDatabase Then
    dataFetcher = New DatabaseDataFetcher()
Else
    dataFetcher = New FileDataFetcher()
End If

DataGridView83.DataSource = dataFetcher.GetData()

The alternative is to just hard-code the file code in that spot. It's a mess and I promise you'll find your life is improved if you use a "classes that implement an interface" approach for this problem every time you solve it.

[smktec]

thanks for input. I guess i will get it to work.