|
|
|
| Title | Let the user drag and drop text to a specific position in a TextBox in VB .NET |
|---|
| Description | This example shows how to let the user drag and drop text to a specific position in a TextBox in VB .NET. |
|---|
| Keywords | drag, drop, drag and drop, TextBox |
|---|
| Categories | Controls |
|---|
|
|
|
When a drag moves over the TextBox, the DragOver event handler calls the TextBoxCursorPos function to see where the cursor is over the TextBox and it places the insertion position there.
If the user drops on the TextBox, the program inserts the dropped text at the current insertion position.
|
|
' If string data is available, allow a copy.
Private Sub TextBox1_DragOver(ByVal sender As Object, ByVal _
e As System.Windows.Forms.DragEventArgs) Handles _
TextBox1.DragOver
If e.Data.GetDataPresent(DataFormats.StringFormat) Then
' Allow the drop.
e.Effect = DragDropEffects.Copy
' Optionally move the cursor position so
' the user can see where the drop would happen.
TextBox1.Select(TextBoxCursorPos(TextBox1, e.X, _
e.Y), 0)
Else
' Do not allow the drop.
e.Effect = DragDropEffects.None
End If
End Sub
' Drop the text into the TextBox.
Private Sub TextBox1_DragDrop(ByVal sender As Object, ByVal _
e As System.Windows.Forms.DragEventArgs) Handles _
TextBox1.DragDrop
TextBox1.SelectedText = _
e.Data.GetData(DataFormats.StringFormat)
End Sub
|
|
|
Function TextBoxCursorPos converts the mouse's coordinates from screen coordinates to the TextBox's coordinate system (both are in pixels). It then sends the EM_CHARFROMPOS message to the TextBox to get the position within the TextBox corresponding to the mouse's position.
sends the Text
|
|
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 = TextBox1.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
|
| |
|
| |
|
|
