Drag-Drop to text box does not work

[Patrick_3]

Hi, for the life of me, I am unable to get my program to drag/drop to a textbox. Elsewhere in my program i am dragging to a panel just fine however I always get the "drag not allowed" mouse symbol when attempting to drag to my text box. I HAVE set the AllowDrop Property of the text box to True and have verified that the DragEnter event is fired and detects the proper data.

Here is my code:

Private Const EM_CHARFROMPOS As Int32 = &HD7
    Private Structure POINTAPI
        Public X As Integer
        Public Y As Integer
    End Structure

    Private Declare Function SendMessageLong Lib "user32" Alias _
        "SendMessageA" (ByVal hWnd As IntPtr, ByVal wMsg As  _
        Int32, ByVal wParam As Int32, ByVal lParam As Int32) As _
        Long

    ' Return the character position under the mouse.
    Public Function TextBoxCursorPos(ByVal txt As TextBox, ByVal X As Single, ByVal Y As Single) As Long
        ' Convert screen coordinates into control coordinates.
        Dim pt As Point = txt.PointToClient(New Point(X, Y))

        ' Get the character number
        TextBoxCursorPos = SendMessageLong(txt.Handle, EM_CHARFROMPOS, 0&, CLng(pt.X + pt.Y * &H10000)) And &HFFFF&
    End Function

    Private Sub Txt_FormatString_DragEnter(sender As Object, e As DragEventArgs) Handles Txt_FormatString.DragEnter
        If e.Data.GetDataPresent(DataFormats.StringFormat) Then
            ' Allow the drop.
            e.Effect = DragDropEffects.Copy
            Trace.WriteLine("I can drag")
        Else
            ' Do not allow the drop.
            e.Effect = DragDropEffects.None
        End If
    End Sub

    ' If string data is available, allow a copy.
    Private Sub Txt_FormatString_DragOver(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles Txt_FormatString.DragOver
        If e.Data.GetDataPresent(DataFormats.StringFormat) Then
            ' Optionally move the cursor position so
            ' the user can see where the drop would happen.
            Txt_FormatString.Select(TextBoxCursorPos(Txt_FormatString, e.X, e.Y), 0)
        End If
    End Sub

    ' Drop the text into the TextBox.
    Private Sub Txt_FormatString_DragDrop(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles Txt_FormatString.DragDrop
        Txt_FormatString.SelectedText = e.Data.GetData(DataFormats.StringFormat)
    End Sub

    Private Sub Lst_DataTypes_ItemDrag(sender As Object, e As ItemDragEventArgs) Handles Lst_DataTypes.ItemDrag
        Dim myItem As ListViewItem
        Dim addString As String

        ' Loop though the SelectedItems collection for the source.
        For Each myItem In sender.SelectedItems
            addString += GetDeliniator() + myItem.SubItems(0).Text
        Next

        ' Create a DataObject containg the array of ListViewItems.
        sender.DoDragDrop(New DataObject(DataFormats.StringFormat, addString), DragDropEffects.Move)
    End Sub

I have no clue why I am not allowed to drag to this text box. Any information is greatly appreciated. Thanks!

[Reverend Jim]

Add this code

Private Sub TextBox1_DragEnter(sender As System.Object, e As System.Windows.Forms.DragEventArgs) Handles TextBox1.DragEnter

    If e.Data.GetDataPresent(DataFormats.FileDrop) Then
        e.Effect = DragDropEffects.All
    End If

End Sub

Private Sub TextBox1_DragDrop(sender As System.Object, e As System.Windows.Forms.DragEventArgs) Handles TextBox1.DragDrop

    If e.Data.GetDataPresent(DataFormats.FileDrop) Then
        Dim files() As String
        files = e.Data.GetData(DataFormats.FileDrop)
        TextBox1.Text = My.Computer.FileSystem.ReadAllText(files(0))
    End If

End Sub

Then try dropping a file on the textbox.

[Reverend Jim]

By the way, I don't know if this is a bug, or just a problem with my installation, but I wanted to implement drag and drop to a rich text box, however, the RichTextBox control did not have an AllowDrop property, or DragEnter or DragDrop events available in the IDE. I had to set AllowDrop manually in the form load and add the handlers manually at the same time using AddHandler.

I just thought I'd mention this is case you ever decide to use a RichTextBox instead of TextBox.

[Patrick_3]

Ok, I added the code you suggested and successfully dragged a file to it; the data did appear in the text box. I don't understand what the issue could be here. I made sure that everything detected the proper data format, it just refuses to allow the drag.

[Reverend Jim]

So are you saying that now it does work (successfully dragged a file to it) or that it doesn't (it just refuses to allow the drag)?

[Patrick_3]

The code you gave works which is for dragging a file. I am trying to drag text from a list view control (I generated the string I want to appear in the text box) to the text box. Basically, your code only with DataFormats.StringFormat. When I attempt to do this, it does not allow me to make the drop.

[Patrick_3]

Do you have any more advice as to what could be the issue?

[Reverend Jim]

I can play around to see what I can come up with but it will have to wait until I finish slogging through my taxes. I should get a chance either later today or tomorrow morning.

[Reverend Jim]

This example implements drag and drop from both ListBox and ListView to a TextBox. The ListView is in Details view.

Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

    For Each word As String In Split("the quick brown fox jumped over the lazy dog")
        ListBox1.Items.Add(word)
        ListView1.Items.Add(New ListViewItem(word))
    Next

End Sub

Private Sub TextBox1_DragEnter(sender As System.Object, e As System.Windows.Forms.DragEventArgs) Handles TextBox1.DragEnter

    If e.Data.GetDataPresent(DataFormats.StringFormat) Then
        e.Effect = DragDropEffects.Copy
    End If

End Sub

Private Sub TextBox1_DragDrop(sender As System.Object, e As System.Windows.Forms.DragEventArgs) Handles TextBox1.DragDrop

    'If empty then add text, else start a new line and add text

    If e.Data.GetDataPresent(DataFormats.StringFormat) Then
        TextBox1.Text &= IIf(TextBox1.Text = "", "", vbCrLf)
        TextBox1.Text &= e.Data.GetData(DataFormats.StringFormat)
    End If

End Sub

Private Sub Listbox1_Mousedown(ByVal Sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles ListBox1.MouseDown
    ListBox1.DoDragDrop(ListBox1.SelectedItems.Item(0), DragDropEffects.Copy Or DragDropEffects.Move)
End Sub

Private Sub ListView1_ItemDrag(sender As System.Object, e As System.Windows.Forms.ItemDragEventArgs) Handles ListView1.ItemDrag
    ListView1.DoDragDrop(ListView1.SelectedItems(0).Text, DragDropEffects.Copy Or DragDropEffects.Move)

End Sub

[Patrick_3]

Thanks to your code, I was finally able to determine what was wrong with mine; it had to do with line 34 of your code

ListView1.DoDragDrop(ListView1.SelectedItems(0).Text, DragDropEffects.Copy Or DragDropEffects.Move)

I was looking for effect 'Copy' but was creating the DoDragDrop with the effect 'Move', VB did not like this. Thanks for all of your help and patience.

[Reverend Jim]

Anytime. The best questions are the ones where I learn something as well.