Devexpress 表格GridView列RepositoryItemPictureEdit异步加载远程URL图片

/// <summary>
/// GridView异步加载url地址的图片,通知CustomColumnDataEventArgs参数
/// </summary>
public class AsynDownImage
{
    private string _URL { get; set; }

    private Bitmap _Image { get; set; }
    private bool _IsReady = false;

    private object _Locker = new object();

    private List<DevExpress.XtraGrid.Views.Base.CustomColumnDataEventArgs> _listens;

    private bool _UseLocalImage = true;//使用本地缓存图片
    public AsynDownImage(string url)
    {
        _UseLocalImage = true;
        _URL = url;
        _listens = new List<DevExpress.XtraGrid.Views.Base.CustomColumnDataEventArgs>();
        this.StartDown();
    }

    /// <summary>
    /// 开始加载图片
    /// </summary>
    void StartDown()
    {
        /*
        //判断本地缓存文件
        if (_UseLocalImage && ImageFileCache.Instance.Exists(ImageBuckleName.small_images, this._URL))
        {
            this._Image = ImageFileCache.Instance.GetImage(ImageBuckleName.small_images, this._URL);
            lock (_Locker)
            {
                _IsReady = true;
            }
            return;
        }
        */

        Task.Run(() =>
        {
            //判断图片路径是否为网络路径
            if (IsUrl(this._URL))
            {
                try
                {
                    //读取文件
                    using (WebClient wc = new WebClient())
                    {
                        Stream tream = wc.OpenRead(this._URL);
                        this._Image = new Bitmap(tream);
                        this._Image = new Bitmap(this._Image, new Size(60, 60));//缩放图片                      
                        /*
                        //缓存图片      
                        if (_UseLocalImage)
                            ImageFileCache.Instance.AddImage(this._URL, this._Image, ImageBuckleName.small_images);
                        */    
                    }
                }
                catch (Exception ex)
                {
                    this._Image = null;
                }
                lock (_Locker)
                {
                    _IsReady = true;
                }
                RunNotify();
                return;
            }
        });
    }


    public void AddListener(DevExpress.XtraGrid.Views.Base.CustomColumnDataEventArgs obj)
    {
        if (this._IsReady)
        {
            obj.Value = this._Image;
        }
        else
        {
            lock (_Locker)
            {
                _listens.Add(obj);
            }
        }
    }
    void refreshCell(DevExpress.XtraGrid.Views.Base.CustomColumnDataEventArgs obj)
    {
        // #002 异步加载，还未加载完成，就把窗体关掉了，造成obj对象为空

        if (obj == null || obj.Column == null || obj.Column.View == null)
                return;
        int handle = obj.Column.View.GetRowHandle(obj.ListSourceRowIndex);
        // #001
        if (handle >= 0)
        {
            if (obj.Column.View is GridView)
            {
                var view = obj.Column.View as GridView;
                view.RefreshRowCell(handle, obj.Column);
            }
            else
            {
                obj.Column.View.RefreshRow(handle);
            }
        }

    }

    void RunNotify()
    {
        lock (_Locker)
        {
            foreach (var obj in _listens)
            {
                refreshCell(obj);
            }
            _listens.Clear();
        }
    }

    /// <summary>
    /// 识别urlStr是否是网络路径
    /// </summary>
    /// <param name="url"></param>
    /// <returns></returns>
    public static bool IsUrl(string url)
    {
        if (Regex.IsMatch(url, @"((http|ftp|https)://)(([a-zA-Z0-9\._-]+\.[a-zA-Z]{2,6})|([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}))(:[0-9]{1,4})*(/[a-zA-Z0-9\&%_\./-~-]*)?"))
        {
            return true;
        }
        else
        {
            return false;
        }
    }

}