c#打印预览控件中实现用鼠标移动页面功能代码分享

[DllImport("user32.dll")]
private static extern int SetScrollPos(IntPtr hwnd, int nBar, int nPos, bool bRedraw);
[DllImport("user32.dll")]
private static extern int GetScrollPos(IntPtr hwnd, int nBar);
[DllImport("user32.dll")]
private static extern bool PostMessage(IntPtr hWnd, int nBar, int wParam, int lParam);
[DllImport("user32", CharSet = CharSet.Auto)]
private static extern bool GetScrollRange(IntPtr hWnd, int nBar, out int lpMinPos, out int lpMaxPos);

private const int SB_HORZ = 0x0;
private const int SB_VERT = 0x1;
private const int WM_HSCROLL = 0x114;
private const int WM_VSCROLL = 0x115;
private const int SB_THUMBPOSITION = 4;

bool Preview_move = false;//是否按下鼠标，表示处理移动状态。
Point MoveStart;//移动开始时，鼠标的坐标点
Point MoveEnd;//移动过程中鼠标的坐标点

private void previewer_MouseDown(object sender, MouseEventArgs e)
{
    Preview_move = true;
    MoveStart = e.Location;
}

private void previewer_MouseUp(object sender, MouseEventArgs e)
{
    Preview_move = false;

private void previewer_MouseMove(object sender, MouseEventArgs e)
{
    if (!Preview_move) return;
    MoveEnd = e.Location;
    int MinH,MaxH,MinV,MaxV;
//获得鼠标在X和Y两个方向上的移动量。除以10是为是让移动页面的速度变慢一点。而前面的负号则是用来调节页面移动方向的。
    int MoveX = -(MoveEnd.X - MoveStart.X)/10;
    int MoveY = -(MoveEnd.Y - MoveStart.Y)/10;
//获取滚动条的最大最小位置和当前位置
    GetScrollRange(previewer.Handle, 0, out MinH, out MaxH);
    GetScrollRange(previewer.Handle, 1, out MinV, out MaxV);
    int PosH = GetScrollPos(previewer.Handle, 0);
    int PosV = GetScrollPos(previewer.Handle, 1);
//计算最终滚动条的位置（注意最终位置不要超出最大最小值的范围）
    int PosH1 = PosH + MoveX;
    if (PosH1 >= MinH && PosH1 <= MaxH)
    {
  SetScrollPos(previewer.Handle, SB_HORZ, PosH1, true);//设置滚动条的位置
  PostMessage(previewer.Handle, WM_HSCROLL, SB_THUMBPOSITION + 0x10000 * PosH1, 0);//告诉控件移动页面内容到相应的位置上
    }

    int PosV1 = PosV + MoveY;
    if (PosV1 >= MinV && PosV1 <= MaxV)
    {
  SetScrollPos(previewer.Handle, SB_VERT, PosV1, true);
  PostMessage(previewer.Handle, WM_VSCROLL, SB_THUMBPOSITION + 0x10000 * PosV1, 0);
    }
}