ListView鼠标框选实现蓝色蒙板

此问题留心已久，今日方悉心求之，记录心得。

ListView控件，不论Delphi中的TListView还是c#中的ListView，在开启其MultiSelect属性时，鼠标框选只是显示框张，如下图示：

相信如系统资源管理器那样，框选以蓝色蒙板显示，视觉效果要好上许多。里外翻阅，发现与LVS_EX_DOUBLEBUFFER标记有关。

根据此线索，改造之。

1、Delphi之TListView

type
  TListView = class(ComCtrls.TListView)
  private
   procedure WMEraseBkgnd(var Message: TWMEraseBkgnd); message WM_ERASEBKGND;
  protected
    procedure CreateWnd; override;
  end;

...

uses
  CommCtrl;

{ TListView }

procedure TListView.CreateWnd;
var
  Styles: DWORD;
begin
  inherited CreateWnd;

  if CheckWin32Version(5, 1) then
  begin
    Styles := ListView_GetExtendedListViewStyle(WindowHandle);
    Styles := Styles or LVS_EX_DOUBLEBUFFER;
    ListView_SetExtendedListViewStyle(WindowHandle, Styles);
  end;
end;

procedure TListView.WMEraseBkgnd(var Message: TWMEraseBkgnd);
begin
  DefaultHandler(Message);
end;

2、c#之ListView

    class ListViewEx : System.Windows.Forms.ListView
    {
        public ListViewEx()
        {
            // 开启双缓冲
            this.SetStyle(ControlStyles.OptimizedDoubleBuffer | ControlStyles.AllPaintingInWmPaint, true);
            UpdateStyles();

            // Enable the OnNotifyMessage event so we get a chance to filter out 
            // Windows messages before they get to the form's WndProc
            this.SetStyle(ControlStyles.EnableNotifyMessage, true);
        }

        protected override void OnNotifyMessage(Message m)
        {
            //Filter out the WM_ERASEBKGND message
            if (m.Msg != 0x14)
                base.OnNotifyMessage(m);
        }
    }

验证实现所需，效果如下图：