How To Drag a Form by a Child Control (154006)

SUMMARY

A window can be moved by clicking the Title bar and then dragging the window to the required position. This technique will not work if the window doesn't have a Title bar. Using the SendMessage API, you can achieve this effect by dragging a control on the form and the form will move with the control. Below is a code sample showing how to accomplish this.

MORE INFORMATION

Start a new project in Visual Basic. Form1 is created by default.
Place a Command button on the form.

Add the following code to the Form1 code window:

   Option Explicit
   Private Declare Sub ReleaseCapture Lib "User" ()
   Private Declare Function SendMessage Lib "User" (ByVal hWnd As _
      Integer, ByVal wMsg As Integer, ByVal wParam As Integer, _
      lParam As Any) As Long

   Private Const WM_SYSCOMMAND = &H112
   Private Const MOUSE_MOVE = &HF012

   ' Enter the line below as one line of code
   Private Sub Command1_MouseDown(Button As Integer, Shift As Integer,  _
   X As Single, Y As Single)
       Dim lReturn As Long
       Call ReleaseCapture
       lReturn = SendMessage(Form1.hWnd, WM_SYSCOMMAND, MOUSE_MOVE, 0)
   End Sub

Press the F5 key to run the project. Note that if you drag the Command button on the screen, the whole form will move with it.

You could remove the Title bar by adjusting the Control box, Caption, and Borderstyle properties of the form and the form can still be dragged by the control.

REFERENCES

For more information, please see the following articles in the Microsoft Knowledge Base:

103062 How to Move Controls at Run Time By Using Drag and Drop

113904 How to Move a Control Across a Form at Run Time

79884 How to Move Controls Between Forms in VB for Windows