Windows Forms Webbrowswer control with IDownloadManager

Question

我正在使用Systems.Windows.Forms.Webbrowser控件，需要覆盖下载管理器。我按照此处的说明对表单进行子类化并覆盖CreateWebBrowserSiteBase()

/// <summary>
/// Browser with download manager
/// </summary>
public class MyBrowser : WebBrowser  
{
    /// <summary>
    /// Returns a reference to the unmanaged WebBrowser ActiveX control site,
    /// which you can extend to customize the managed <see ref="T:System.Windows.Forms.WebBrowser"/> control.
    /// </summary>
    /// <returns>
    /// A <see cref="T:System.Windows.Forms.WebBrowser.WebBrowserSite"/> that represents the WebBrowser ActiveX control site.
    /// </returns>
    protected override WebBrowserSiteBase CreateWebBrowserSiteBase()
    {
        var manager = new DownloadWebBrowserSite(this);
        manager.FileDownloading += (sender, args) =>
            {
                if (FileDownloading != null)
                {
                    FileDownloading(this, args);
                }
            };
        return manager;
    }
}

在DownloadWebBrowserSite中，我实现了IServiceProvider以在请求时提供IDownloadManager。

        /// <summary>
        /// Queries for a service
        /// </summary>
        /// <param name="guidService">the service GUID</param>
        /// <param name="riid"></param>
        /// <param name="ppvObject"></param>
        /// <returns></returns>
        public int QueryService(ref Guid guidService, ref Guid riid, out IntPtr ppvObject)
        {
            if ( (guidService == Constants.IID_IDownloadManager && riid == Constants.IID_IDownloadManager ))
            {
                ppvObject = Marshal.GetComInterfaceForObject(_manager, typeof(IDownloadManager));
                return Constants.S_OK;
            }
            ppvObject = IntPtr.Zero;
            return Constants.E_NOINTERFACE;
        }

DownloadManager取自上面的示例。

/// <summary>
/// Intercepts downloads of files, to add as PDFs or suppliments
/// </summary>
[ComVisible(true)]
[Guid("bdb9c34c-d0ca-448e-b497-8de62e709744")]
[CLSCompliant(false)]
public class DownloadManager : IDownloadManager
{
    /// <summary>
    /// event called when the browser is about to download a file
    /// </summary>
    public event EventHandler<FileDownloadEventArgs> FileDownloading;
    /// <summary>
    /// Return S_OK (0) so that IE will stop to download the file itself. 
    /// Else the default download user interface is used.
    /// </summary>
    public int Download(IMoniker pmk, IBindCtx pbc, uint dwBindVerb, int grfBINDF, IntPtr pBindInfo,
                        string pszHeaders, string pszRedir, uint uiCP)
    {
        // Get the display name of the pointer to an IMoniker interface that specifies the object to be downloaded.
        string name;
        pmk.GetDisplayName(pbc, null, out name);
        if (!string.IsNullOrEmpty(name))
        {
            Uri url;
            if (Uri.TryCreate(name, UriKind.Absolute, out url))
            {
                if ( FileDownloading != null )
                {
                     FileDownloading(this, new FileDownloadEventArgs(url));
                }
                return Constants.S_OK;
            }
        }
        return 1;
    }
}

问题是pmk.GetDisplayName返回的是初始 URL，而不是要下载的项目的 URL。如果 URI 指向动态页面（如 http://www.example.com/download.php），则我无法下载要下载的实际文件。我需要从标头中获取URL，以便获得应该下载的实际文件。

Google表示我必须创建一个IBindStatusCallback实现，该实现也实现了IHttpNegotiate和IServiceProvider以响应IID_IHttpNegotiate，以便我可以看到IHttpNegotiate.OnResponse。我已经设法实现了它，但是，QueryService似乎只要求IID_IInternetProtocol而从未IID_IHttpNegotiate。

任何建议都会很棒。

Answer 1

您错过了对以下的调用：CreateBindCtx。

将以下内容添加到您的下载管理器：

   [DllImport("ole32.dll")]
        static extern int CreateBindCtx(uint reserved, out IBindCtx ppbc);

然后，请确保在注册回调之前调用此呼叫。我已经在您的 Download（） 方法中实现了这一点，如下所示：

public int Download(IMoniker pmk, IBindCtx pbc, uint dwBindVerb, int grfBINDF, IntPtr pBindInfo,
                            string pszHeaders, string pszRedir, uint uiCP)
        {
            // Get the display name of the pointer to an IMoniker interface that specifies the object to be downloaded.
            string name;
            pmk.GetDisplayName(pbc, null, out name);
            if (!string.IsNullOrEmpty(name))
            {
                Uri url;
                if (Uri.TryCreate(name, UriKind.Absolute, out url))
                {
                    Debug.WriteLine("DownloadManager: initial URL is: " + url);
                    CreateBindCtx(0, out pbc);
                    RegisterCallback(pbc, url);
                    BindMonikerToStream(pmk, pbc);
                    return MyBrowser.Constants.S_OK;
                }
            }
            return 1;
        }

完成此操作后，将调用 IHttpNegotiate 实现，并且你将有权访问响应标头。