Sunday, 16 January 2011

Just started looking at Windows Workflow Foundation (WF) 4

I’ve just started looking at the Windows Workflow Foundation 4. Now in it’s fourth Generation, the Windows Workflow Foundation, or WF for short, is a completely different way to go about Programming.

WF allows a programmer to create applications using a graphical approach, such as Flowcharts, Sequence Diagrams and State Machines.

Complex programs can be created direct on a xaml designer workspace with very little in the way of lines of code.

I’ve been following a great series of screencasts by DevelopMentor instructor, freelance developer and MVP Maurice de Beijer.

In these screencasts, Maurice takes you through from beginning your first “Hello World” (or “Hello workflow” maybe?), all the way through to creating custom activity and error handling.

The Screencast series can be found here;

http://msdn.microsoft.com/en-us/netframework/dd733248

One thing which is missing from the series are the code samples however, so I’ve uploaded the code for first five Screencasts to my website in case anyone needs them. They’re available here…

http://www.pjgcreations.co.uk/public/WFScreenCasts/

Note however that, as a I am a VB.net programmer, these Code Samples are all in VB.net, however Maurice has chosen to use C#.

This isn’t a major problem as there’s not a massive amount of actual coding involved, and most of the code is very similar anyhow.

But, if you do need the C# version, I highly recommend you use the following free website to convert VB.net code to C#;

http://www.developerfusion.com/tools/convert/csharp-to-vb/

.EndEdit causes row movement of a sorted BindingSource

When applying a sort to a Database BindingSource, executing the BindingSource.EndEdit method causes the currently selected row to change.

This has the effect of reloading any bound controls when tee edited row is saved, which of course can have unwanted effects if you need to operating on data related to the currently selected row after the EndEdit has been performed.

This issue can also be observed to a degree by selecting a row in a bound DataGrid, then choose the sorted column. It can be seen that the physical location of the selected row doesn’t change, however the previously selected row has now moved.

There are a number of ways to deal with the EndEdit issue, one of which  I found here…

http://social.msdn.microsoft.com/Forums/en/winformsdatacontrols/thread/0878567a-ccb1-441b-a51d-3e014372e61b

Where we check the ListChanged event and the e.ListChangeType;

Private Sub bsBindingSource_ListChanged(ByVal sender As Object, ByVal e _

    As System.ComponentModel.ListChangedEventArgs) Handles _

    bsBindingSource.ListChanged

    If e.ListChangedType = _

        System.ComponentModel.ListChangedType.ItemMoved Then

        bsBindingSource.Position = e.NewIndex

    End If

End Sub

Another method is to store the current state of the form, i.e. editing, adding, duplicating, normal etc in an enum. then use the following code;

Private Sub bsBindingSource_ListChanged(ByVal sender As Object, ByVal e _

    As System.ComponentModel.ListChangedEventArgs) Handles _

    bsBindingSource.ListChanged

    If sttCurrentFormState = Normal Then

        bsBindingSource.Position = e.NewIndex

    End If

End Sub