如何读取 HttpWebResponse 两次

Question

如何读两遍

HttpWebResponse

？有可能吗？

我的代码不起作用，

respStream.Position = 0;

没有帮助。

请问有什么线索吗？

var data = (HttpWebRequest)WebRequest.Create(url);  
var response = (HttpWebResponse)data.GetResponse();

var respStream = response.GetResponseStream();
            
string responseText;         
using (var reader = new StreamReader(respStream, encoding))
{
     responseText = reader.ReadToEnd().Trim();
}
// Do something and read it again
using (var reader = new StreamReader(respStream, encoding))
{
     responseText = reader.ReadToEnd().Trim();
}

Answer 1

从

response.GetResponseStream()

返回的类型是

System.Net.ConnectStream

。如果你检查这个流的属性

CanSeek

，你会发现它无法被查找，所以这意味着你无法重置它并再次读取它：

var typeOfStream = respStream.GetType();    // System.Net.ConnectStream
var canSeek = respStream.CanSeek;           // false

但是，当您将数据读取到字符串时，您已经拥有了数据，因此您可以使用它两次：

string responseText1, responseText2;
using (var reader = new StreamReader(respStream, encoding))
{
     responseText1 = reader.ReadToEnd().Trim();
     responseText2 = responseText1;    // you get a copy of response
}

Answer 2

我遇到了类似的问题，但我的流不包含字符串内容，而是包含二进制数据。由于我们只能读取 ConnectStream 一次，所以我的解决方案是将其复制到 MemoryStream：

WebRequest request = WebRequest.Create("http://www.foo.bar/binary.file");
using (WebResponse response = request.GetResponse())
{
    var responseStream = response.GetResponseStream();

    using (var memoryStream = new MemoryStream())
    {
        responseStream.CopyTo(memoryStream);

        // This one is important so we can read the stream from the beginning.
        memoryStream.Seek(0, SeekOrigin.Begin); 

        // Perform my first thing.
        var isValid = Utility.ValidateContent(memoryStream);

        if (isValid)
        {
            // Reset the position to the beginning of the stream again
            memoryStream.Seek(0, SeekOrigin.Begin); 
            using (var fileStream = File.Create("c:\\temp\\myfile.ext"))
            {
                memoryStream.CopyTo(fileStream);
            }
        }
    }
}

需要明确的是，如果只需要两倍的字符串数据，“dotnetom”提供的解决方案会更干净、更快。