Parsing HTTP POST with StreamReader (multipart/form-data with file)

I am attempting to parse an HTTP POST (from a NetworkStream) that is multipart/form-data with a file input field.

The problem is that I need to parse the stream with a StreamReader in order to parse the header/boundary strings, but the file itself is raw binary data in the middle of this string. I cannot figure out how to mix StreamReader and raw memory access to write this file out to the disk, because the ASCII encoding/decoding is trashing information in the binary data.

I need a way to mix text parsing with raw memory access. My best attempt is to copy the POST to a MemoryStream, use the stream reader, and remember the stream position when the boundarys are found. However, the StreamReader reads in 1024 byte increments, so this is not useful. I have not found a way to find the precise offset within the buffer that StreamReader is located.

Any ideas on how to parse this data?

I am using .NET 3.0 with Visual C# 2008.

Code:

---


            using (BinaryReader breader = new BinaryReader(stream))
            {
                  ///find tags etc here
                using (StringReader sreader = new StringReader(breader.ReadString()))
                {
                    //Parse this as a string
                }
            }

---

That does not seem very useful because BinaryReader.ReadString needs a special format of string to know how many characters to read. This data is coming from a web client that I have no control over, I cannot rely on special formats like that.

Then I suppose you are going to have to do it the hard way, by reading each character as a char and adding it into a StringBuilder. Then you can use the StringReader class.