C# Signature:
[DllImport("user32.dll")]
static extern bool ReleaseCapture();
VB.NET Signature:
<DllImport("user32.dll")> _
Private Shared Function ReleaseCapture() As Boolean
End Function
User-Defined Types:
None.
Notes:
None.
ReleaseCapture will delegate mousedown events to underlying controls.
Tips & Tricks:
Create a form without a title bar and can be moved by mouse.
'const and dll functions for moving form
Public Const WM_NCLBUTTONDOWN As Integer = &HA1
Public Const HT_CAPTION As Integer = &H2
<DllImport("user32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> _
Private Shared Function SendMessage(ByVal hWnd As IntPtr,
ByVal Msg As UInteger,
ByVal wParam As IntPtr,
ByVal lParam As IntPtr) As IntPtr
End Function
<DllImportAttribute("user32.dll")> _
Public Shared Function ReleaseCapture() As Boolean
End Function
Private Sub Form1_MouseDown(sender As Object, e As MouseEventArgs) Handles Me.MouseDown
If e.Button = MouseButtons.Left Then
ReleaseCapture()
SendMessage(Handle, WM_NCLBUTTONDOWN, HT_CAPTION, 0)
End If
End Sub
Sample Code:
You can use the ReleaseCapture() function to provide drag functionality. for example the following code will allow the user to drag a control around a form (you'll have to assign this code to the mousedown event):
[DllImport("User32.dll")]
private static extern int SendMessage(IntPtr hWnd, int msg , int wParam , ref int lParam);
[DllImport("user32")]
public static extern bool ReleaseCapture(IntPtr hwnd);
private const int WM_SYSCOMMAND = 0x112;
private const int MOUSE_MOVE = 0xF012;
private void control_MouseDown(object sender, MouseEventArgs e)
{
Control ctrl = sender as Control;
ReleaseCapture(ctrl.Handle);
int nul =0;
SendMessage(ctrl.Handle, WM_SYSCOMMAND, MOUSE_MOVE, ref nul);
}
Alternative Managed API:
Capture property on System.Windows.Forms.Control
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