.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.

Ive never really done any dragdrop in this manner in VB6 so Im not very sure how to initialize a drag. Thanks for any help!

 

[Derek Stone]

Example

The example below should get you going.

 

[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, Im getting the following error:

Run-timer error 461:

Specified format doesnt 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? Im not too sure what this error means.

 

[Derek Stone]

To be perfectly honest Ive never used drag and drop across two different languages, so Im not sure if itll 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

Im 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 cant 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