How to make a control resizable by the user at runtime [.NET Winforms]?

Question

It is in Winforms.

I have a UserControl that is anchored TOP, BOTTOM and LEFT. I would like to allow the user to drag its right border somehow and resize it horizontally.

The control is placed right into the form, no panel or groupbox to place a "Splitter".

Any idea how to make a control resizable at runtime by the user?

Answer 1

Private Declare Function GetWindowLongA Lib "User32" (ByVal hWnd As Integer, ByVal nIndex As Integer) As Long
Private Declare Function SetWindowLongA Lib "User32" (ByVal hWnd As Integer, ByVal nIndex As Integer, ByVal dwNewLong As Long) As Long
Private Declare Sub SetWindowPos Lib "User32" (ByVal hWnd As Integer, ByVal hWndInsertAfter As Integer, ByVal X As Integer, ByVal Y As Integer, ByVal CX As Integer, ByVal CY As Integer, ByVal wFlags As Integer)
Const SWP_NOSIZE = &H1
Const SWP_NOZORDER = &H4
Const SWP_NOMOVE = &H2
Const SWP_DRAWFRAME = &H20
Const GWL_STYLE = (-16)
Const WS_THICKFRAME = &H40000

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    ResizeControl(TextBox1, Me)
End Sub

Sub ResizeControl(ByVal ControlName As Control, ByVal FormName As Form)
    Dim NewStyle As Long
    NewStyle = GetWindowLongA(ControlName.Handle, GWL_STYLE)
    NewStyle = NewStyle Or WS_THICKFRAME
    NewStyle = SetWindowLongA(ControlName.Handle, GWL_STYLE, NewStyle)
    SetWindowPos(ControlName.Handle, FormName.Handle, 0, 0, 0, 0, SWP_NOZORDER Or SWP_NOSIZE Or SWP_NOMOVE Or SWP_DRAWFRAME)
End Sub