我有一个数据：URI，我需要下载（读：负荷流或字节数组），使用普通的.Net Web客户端 / 的WebRequest 。我该怎么办呢？

I have a data: URI that I need to "download" (read: load as a stream or byte array) using the normal .Net WebClient/WebRequest. How can I do that?

我需要这个，因为我需要显示SVG，其中包括使用的数据有些图像生成的XAML文件：URI的。我不想总是解析XAML，保存图像到磁盘，然后更改XAML指向的文件。我相信WPF使用的WebRequest 内部获得的图像。

I need this because I want to display a XAML file generated from SVG, which includes some images using data: URIs. I don't want to always parse the XAML, save the images to disk and then change the XAML to point to the files. I believe WPF uses WebRequest internally to get those images.

推荐答案

您可以使用的 WebRequest.Register preFIX（） 做到这一点。您将需要实施 IWebRequestCreate 返回一个自定义的的WebRequest 返回一个自定义的 WebResponse类，系统可最终用于获取从URI中的数据。它可能是这样的：

You can use WebRequest.RegisterPrefix() to do that. You will need to implement IWebRequestCreate that returns a custom WebRequest that returns a custom WebResponse, which can finally be used to get the data from the URI. It could look like this:

public class DataWebRequestFactory : IWebRequestCreate
{
    class DataWebRequest : WebRequest
    {
        private readonly Uri m_uri;

        public DataWebRequest(Uri uri)
        {
            m_uri = uri;
        }

        public override WebResponse GetResponse()
        {
            return new DataWebResponse(m_uri);
        }
    }

    class DataWebResponse : WebResponse
    {
        private readonly string m_contentType;
        private readonly byte[] m_data;

        public DataWebResponse(Uri uri)
        {
            string uriString = uri.AbsoluteUri;

            int commaIndex = uriString.IndexOf(',');
            var headers = uriString.Substring(0, commaIndex).Split(';');
            m_contentType = headers[0];
            string dataString = uriString.Substring(commaIndex + 1);
            m_data = Convert.FromBase64String(dataString);
        }

        public override string ContentType
        {
            get { return m_contentType; }
            set
            {
                throw new NotSupportedException();
            }
        }

        public override long ContentLength
        {
            get { return m_data.Length; }
            set
            {
                throw new NotSupportedException();
            }
        }

        public override Stream GetResponseStream()
        {
            return new MemoryStream(m_data);
        }
    }

    public WebRequest Create(Uri uri)
    {
        return new DataWebRequest(uri);
    }
}

这仅支持base64编码，但对于URI编码的支持，可以很容易地补充说。

This supports only base64 encoding, but support for URI encoding could be easily added.

然后注册它是这样的：

WebRequest.RegisterPrefix("data", new DataWebRequestFactory());

是的，这确实检索数据的工作：XAML文件中的图片

And yes, this does work for retrieving data: images in XAML files.