Using the clipboard


Sorry that I have not made a post in a while, but I have been very busy at work lately fixing bugs in the Whidbey object model, as well as working to get a new way of writing wizards ready (more info on that in a few days).


 


Not too long ago I was browsing the net, and found a code snip that I sent to somebody describing how to use the clipboard from a macro. Because of the way the Macros IDE runs macros on behalf of Visual Studio, there are some problems when trying to access some features of the .NET frameworks. An example of this problem is when trying to access the clipboard. If you were to run this code:


 


    Sub GetCBData()


        Dim o As System.Windows.Forms.IDataObject


        Dim s As String


        o = System.Windows.Forms.Clipboard.GetDataObject()


        s = o.GetData(System.Windows.Forms.DataFormats.StringFormat)


        MsgBox(s)


    End Sub


 


You would get back an “Object reference not set to an instance of an object.” exception. How do you work around it? You will need to create a new thread, and set the clipboard from within that thread. Here is a class to do just such a thing:


 


Public Class MacroClipBoard


    Dim str As String


 


    Function GetFromProxy() As String


        Dim t As New System.Threading.Thread(AddressOf GetFrom)


        t.Start()


        t.Join()


        Return str


    End Function


 


    Sub CopyToProxy(ByVal s As String)


        str = s


        Dim t As New System.Threading.Thread(AddressOf CopyTo)


        t.Start()


        While (t.IsAlive)


            ‘Do nothing. Wait for the thread to do its work.


        End While


        t.Join()


    End Sub


 


    Sub GetFrom()


        Dim o As System.Windows.Forms.IDataObject


        o = System.Windows.Forms.Clipboard.GetDataObject()


        str = o.GetData(System.Windows.Forms.DataFormats.StringFormat)


    End Sub


 


    Sub CopyTo()


        System.Windows.Forms.Clipboard.SetDataObject(str, True)


    End Sub


 


End Class


 


To use this class, you would run code such as this:


 


    Sub testcb()


        Dim macroCB As New MacroClipBoard


        macroCB.CopyToProxy(“Some random string”)


        MsgBox(macroCB.GetFromProxy)


    End Sub


 


This code only works with string data types, but you could easily modify it to return other types such as bitmaps.


 


Edit 2/16: I made a small change to the CopyToProxy function, replacing the strike-through text with “t.Join()”

Comments (13)

  1. Mike Dimmick says:

    OK, dumb question: why can’t CopyToProxy simply call t.Join, rather than spinning on t.IsAlive?

  2. Woo Seok Seo says:

    Could you tell me why I need to create a thread?

  3. Craig says:

    Why didn’t I use t.Join? Because when I wrote the code it was immediately returning, leaving str unassigned. I put that loop in there to watch the variable to see when it was being set, but never switched my code over. Doh!

  4. Craig says:

    The reason this happens is that the clipboard code in the URT wants the caller to be single threaded. Macros, however, run in a multi-threaded environment. The two threading models conflict and the exception is generated.

  5. Koji Ishii says:

    I can barely understand this is STA problem, but I don’t understand why this code works. This code creates more threads, and calls SetDataObject from non-UI thread. I’m curious why making yet another thread, which is apparently non-UI, not having message-pump, thread helps this problem. Any further explanations would be appreciated.

  6. peterhcy says:

    Could you tell me how to install and set up a blog?

  7. Drax says:

    This information is really usefull!!! thanks a lot!!!

  8. Jeff Atwood says:

    Note that in VS.NET you *MUST* set the threadingmodel for the thread to STA explicitly:

    Dim t As New Threading.Thread(AddressOf GetClipboardPrivate)

    t.ApartmentState = Threading.ApartmentState.STA

    t.Start()

    t.Join()

  9. Jeff Atwood says:

    Sorry, I meant in VS.NET *2005*. That’s required now..

  10. hmt says:

    Thank you! The just the answer I’ve been looking for!

  11. hmt says:

    Thank you! This is the answer I’ve been looking for!

  12. dorasoft says:

    I used code

    Dim t As New Threading.Thread(AddressOf CPKeyPress)

    t.ApartmentState = Threading.ApartmentState.STA

    t.Start()

    t.Join()

    But there was error :

    Overload resolution failed because no accessible ‘New’ can be called with these arguments:

       ‘Public Sub New(start As System.Threading.ParameterizedThreadStart)’: Method ‘Private Sub CPKeyPress(sender As Object, HotKey As HotKey)’ does not have a signature compatible with delegate ‘Delegate Sub ParameterizedThreadStart(obj As Object)’.

       ‘Public Sub New(start As System.Threading.ThreadStart)’: Method ‘Private Sub CPKeyPress(sender As Object, HotKey As HotKey)’ does not have a signature compatible with delegate ‘Delegate Sub ThreadStart()’. D:ProjectOffice AssistantFormfrmMain.vb 80 13 OfficeAssistant

  13. Warez says:

    Thanks for the Info is really usefull!!! thanks a lot!!!

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