CefSharp解决无法下载（不弹出保存框）的问题

解决方案：

在相关文件下继承并实现IDownloadHandler中OnBeforeDownload和OnDownloadUpdated方法即可，代码如下：

public class DownloadHandler : IDownloadHandler
{
    public event EventHandler<DownloadItem> OnBeforeDownloadFired;
    public event EventHandler<DownloadItem> OnDownloadUpdatedFired;

    public void OnBeforeDownload(IWebBrowser chromiumWebBrowser, IBrowser browser, DownloadItem downloadItem, IBeforeDownloadCallback callback)
    {
        OnBeforeDownloadFired?.Invoke(this, downloadItem);
        if (!callback.IsDisposed)
        {
            using (callback)
            {
                callback.Continue(downloadItem.SuggestedFileName, showDialog: true);
            }
        }
    }

    public void OnDownloadUpdated(IWebBrowser chromiumWebBrowser, IBrowser browser, DownloadItem downloadItem, IDownloadItemCallback callback)
    {
        OnDownloadUpdatedFired?.Invoke(this, downloadItem);
    }
}