扩展WebBrowser控件，使其支持拖放文件

浏览数：15 / 时间：2015年06月09日

public 
partial 
class 
UserControl1 : WebBrowser
{
    private 
const 
int 
WmDropfiles = 0x233;
 
    [DllImport("shell32.dll")]
    private 
static 
extern 
uint 
DragQueryFile(IntPtr hDrop, uint 
iFile, StringBuilder lpszFile, uint 
cch);
 
    [DllImport("shell32.dll")]
    private 
static 
extern 
void 
DragAcceptFiles(IntPtr hWnd, bool 
fAccept);
 
    protected 
override 
void 
OnHandleCreated(EventArgs e)
    {
        base.OnHandleCreated(e);
 
        //指示接受文件拖放操作
        if 
(!DesignMode)
        {
            DragAcceptFiles(Handle, true);
        }
    }
 
    protected 
override 
void 
WndProc(ref 
Message m)
    {
        if 
(m.Msg == WmDropfiles)
        {
            #region 解析消息
            //获取拖放的文件数量
            var 
count = DragQueryFile(m.WParam, 0xffffffff, null, 0);
            //解析所有播放的文件路径
            var 
filePaths = new 
string[count];
            for 
(uint 
i = 0; i < count; i++)
            {
                var 
sb = new 
StringBuilder();
                DragQueryFile(m.WParam, i, sb, 1024);
                filePaths[i] = sb.ToString();
            }
            #endregion
 
            //是否继续触发之后的消息处理
            var 
isCancel = false;
 
            #region 触发自定义文件拖放事件
            if 
(DragFile != null)
            {
                var 
args = new 
DragFileEventArgs(filePaths);
                DragFile(this, args);
                isCancel = args.IsCancel;
            }
            #endregion
 
            if 
(isCancel) return;
        }
        base.WndProc(ref 
m);
    }
 
    public 
event 
EventHandler<DragFileEventArgs> DragFile;
 
    public 
class 
DragFileEventArgs : EventArgs
    {
        private 
readonly 
string[] _filePaths;
        public 
bool 
IsCancel { get; set; }
 
        public 
DragFileEventArgs(string[] filePaths)
        {
            _filePaths = filePaths;
        }
 
        public 
string[] FilePaths
        {
            get 
{ return 
_filePaths; }
        }
    }
}