.Net Framework 3.5及更低版本中，CopyTo（）和WriteTo（）的等效方法是什么？

Question

I need to use .NetFramework3.5 for my application, but CopyTo() and WriteTo() methods are not available in 3.5. what are the equivalent methods in 3.5?

when I run the code with 3.5 it is throwing the following error:

'System.IO.Stream' does not contain a definition for 'WriteTo' and no extension method 'WriteTo' accepting a first argument of type 'System.IO.Stream' could be found

Here is the code:

int fileId = 1;
foreach (string uri in uriList)
{

    request = (HttpWebRequest)WebRequest.Create (baseURL + uri);
    request.Headers.Add ("X", authenticateStr);
    request.Accept = "application/pdf";
    request.Method = "GET";

    webResponse = (HttpWebResponse)request.GetResponse();
    using (MemoryStream ms = new MemoryStream())
    using (FileStream outfile = new FileStream("document_", FileMode.Create)) {
        webResponse.GetResponseStream().WriteTo(ms);
        if (ms.Length > int.MaxValue) {
            throw new NotSupportedException("Cannot write a file larger than 2GB.");
        }
        outfile.Write(ms.GetBuffer(), 0, (int)ms.Length);
    }
}
Console.WriteLine("Done!");

Answer 1

1. Stream.CopyTo was indeed added with .NET 4. Earlier versions of .NET are missing lots of helpful methods added in latter versions. .NET 4.5 continues to have lots of "obvious" method missing, I assume future versions will continue to add such helpers if MS perceive sufficient demand.

2. There is no Stream.WriteTo . It only exists on some subclasses (eg. MemoryStream.WriteTo which has existed since .NET 1.0).

(I suspect Stream.CopyTo was added as a common MemoryStream.WriteTo but obviously using WriteTo would be an API breaking change because, for example, reflection on it would give different results.)

Answer 2

If you need for CopyTo I use this extension

public static void CopyTo(this Stream input, Stream output)
{
   // This method exists only in .NET 4 and higher

   byte[] buffer = new byte[4 * 1024];
   int bytesRead;

   while ((bytesRead = input.Read(buffer, 0, buffer.Length)) != 0)
   {
      output.Write(buffer, 0, bytesRead);
   }
}