vb.net 实现无标题栏窗体拖拽功能

<pre name="code" class="vb">'较好用，没有闪动  
  Declare Auto Function ReleaseCapture Lib "user32.dll" Alias "ReleaseCapture" () As Boolean
    'API ReleaseCapture函数是用来释放鼠标捕获的
    Declare Auto Function SendMessage Lib "user32.dll" Alias "SendMessage" (ByVal hWnd As IntPtr, ByVal wMsg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) As IntPtr
    '向windows发送消息
    Public Const WM_SYSCOMMAND As Integer = &H112&
    Public Const SC_MOVE As Integer = &HF010&
    Public Const HTCAPTION As Integer = &H2&
Private Sub frm1_MouseMove(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseMove
        If e.Button = MouseButtons.Left Then
            ReleaseCapture()
            SendMessage(Me.Handle, WM_SYSCOMMAND, SC_MOVE + HTCAPTION, 0)
        End If


    End Sub

'这种方法会造成鼠标点一下窗体瞬间移动到某处，有闪动现象
    Private mouseOffset As Point
    '记录鼠标指针的坐标  
    Private isMouseDown As Boolean
    Private Sub frm1_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseDown


        Dim xOffset As Integer
        Dim yOffset As Integer


        If (e.Button = MouseButtons.Left) Then
            xOffset = -e.X - SystemInformation.FrameBorderSize.Width
            yOffset = -e.Y - SystemInformation.CaptionHeight - SystemInformation.FrameBorderSize.Height
            mouseOffset = New Point(xOffset, yOffset)
            isMouseDown = True
        End If


    End Sub


    Private Sub frm1_MouseMove(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseMove


        If (isMouseDown) Then
            Dim mousePos As Point = Control.MousePosition
            mousePos.Offset(mouseOffset.X, mouseOffset.Y)
            Location = mousePos
        End If


    End Sub


    Private Sub frm1_MouseUp(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseUp
        If (e.Button = MouseButtons.Left) Then
            isMouseDown = False
        End If
    End Sub