.NET OleDragDrop

[Audax321]

VB6 had oleDragDrop, what is the equivalent in .NET and how do you use it?

 

I have an application that searches user selected directories for files that match a search string. I want to allow the user to drag a line from the search results that appear in a listbox to another application. The drag must contain the path to the file being dragged.

 

I've never really done any dragdrop in this manner in VB6 so I'm not very sure how to initialize a drag. Thanks for any help! :)

[Derek Stone]

Example

 

The example below should get you going.

windowsapplication2.zip

[Audax321]

Okay, I got the drag to initialize. The problem I am having now is getting the drag into my other program which is made in VB6. The string containing the path is being dragged into a listview control on the other application. But, I'm getting the following error:

 

Run-timer error '461':

 

Specified format doesn't match format of data

 

My other application accepts files using the data.files array. So is there anyway to get the path to be added to this when the drag is initialized? If not, then how do I get the other application to read the string? I'm not too sure what this error means.

[Derek Stone]

To be perfectly honest I've never used drag and drop across two different languages, so I'm not sure if it'll even work, especially due to the different nature of .NET. Are you passing the data using a text/string format and are you receiving the data using the same format?

[Audax321]

Here is the code initializing the drag:

 

Private Sub lstResults_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles lstResults.MouseDown
       If (lstResults.Items.Count > 0 And lstResults.SelectedIndex < lstResults.Items.Count) Then
           lstResults.DoDragDrop(lstPath.Items.Item(lstResults.SelectedIndex) & lstResults.Items.Item(lstResults.SelectedIndex), DragDropEffects.Copy)
       End If
   End Sub

 

and here is the code that process the drag in the other program:

 

Private Sub lstPlaylist_OLEDragOver(Data As MSComctlLib.DataObject, Effect As Long, Button As Integer, Shift As Integer, x As Single, y As Single, State As Integer)
   If (Button = vbLeftButton) Then
       DragOpen = False
   Else
       DragOpen = True
   End If
End Sub

Private Sub lstPlaylist_OLEDragDrop(Data As MSComctlLib.DataObject, Effect As Long, Button As Integer, Shift As Integer, x As Single, y As Single)
   On Error GoTo Drophandler
   
   If (Data.Files.Count > 0) Then
       MsgBox ("drag initiated")
   
       For Each DragFile In Data.Files
           intstrsearch = InStr(1, DragFile, ".")
       
           Do While (intstrsearch < InStr(intstrsearch + 1, DragFile, "."))
               If (intstrsearch < InStr(intstrsearch + 1, DragFile, ".")) Then
                   intstrsearch = InStr(intstrsearch + 1, DragFile, ".")
               End If
           Loop

           strFileToOpen = Mid(DragFile, intstrsearch + 1, Len(DragFile))
           
           If (strFileToOpen = "mp3" Or strFileToOpen = "mp2" Or strFileToOpen = "m3u" _
               Or strFileToOpen = "mpg" Or strFileToOpen = "mpeg" Or strFileToOpen = "mpe" _
               Or strFileToOpen = "mlv" Or strFileToOpen = "mpv2" Or strFileToOpen = "mp2v" _
               Or strFileToOpen = "mpa" Or strFileToOpen = "cda" Or strFileToOpen = "au" _
               Or strFileToOpen = "aif" Or strFileToOpen = "aifc" Or strFileToOpen = "aiff" _
               Or strFileToOpen = "ivf" Or strFileToOpen = "wav" Or strFileToOpen = "avi" _
               Or strFileToOpen = "mid" Or strFileToOpen = "midi" Or strFileToOpen = "rmi" _
               Or strFileToOpen = "wmv" Or strFileToOpen = "wvx" Or strFileToOpen = "wma" _
               Or strFileToOpen = "wax" Or strFileToOpen = "asf" Or strFileToOpen = "asx" _
               Or strFileToOpen = "wm" Or strFileToOpen = "wmx" Or strFileToOpen = "wmp") Then
               
               strFileToOpen = DragFile
           
               If (DragOpen = False) Then
                   Call CommandAddFiles
               End If
           
               If (DragOpen = True) Then
                   Call CommandOpenFiles
               End If
           End If
       Next
       
       Data.Files.Clear
   End If

Drophandler:
   MsgBox ("the drop was lost")
End Sub

 

I'm sure there is some way to do this, because it would be very counter productive for Microsoft to not allow .NET and VB6 applications to communicate in this way. The thing is that I really suck at this dragdrop stuff. I just wrote that code for the dragdrop procedure in the VB6 app a few days ago. It works great if you drag from Explorer, but I can't get it to work with the .NET application.

[Audax321]

The drag is being initialized with a string but is being processed using drag.files which is an array of strings that point to paths to files. I have to get .NET to add its string to this array like Explorer does... I think :)

[Audax321]

I figured it out.... I was assuming that visual basic would consider the dragged string a file because it was a path. Instead, I got it to work by having vb6 handle it as a string. Then to make sure that the string was a file, I just evaluted the following:

 

len(dir(draggedstring))

 

If its not 0 then the program processes it. Hope it helps someone else... I was complicating things for myself for no good reason LOL :)

Edited December 5, 2002 by Audax321