Using Streams in C#

Question

I'm interested in pulling a file from online a .txt file.

The txt file stores:

filename md5 hash filename md5 hash

I am interested in getting the data from online then comparing the data to local files.

        byte[] buffer = new byte[512];
        WebRequest test = WebRequest.Create("http://www.domain.com/file.txt");
        Stream something = test.GetRequestStream();
        something.Read(buffer,0,20);

I don't quite understand streams and how to go about reading just one line from the file. I do not want to download the file first then retrieve the data. I'm interested in just pulling it from online. How different are "streams" vs normal IO, with StreamWriter and StreamReader?

EDIT--

       WebRequest myWebRequest = WebRequest.Create("http://www.domain.com/file.txt");

       WebResponse myReponse = myWebRequest.GetResponse();

       Stream recStream = myReponse.GetResponseStream();

       StreamReader reader = new StreamReader(recStream);

       txt_status.Text = reader.ReadLine();

Aaron McIver · Accepted Answer · 2011-01-19 19:36:10Z

2

GetRequestStream provides a stream for writing to. If you want the returned data to walk through make use of GetResponseStream

...

Stream ReceiveStream = myWebResponse.GetResponseStream();

    Encoding encode = System.Text.Encoding.GetEncoding("utf-8");

        // Pipe the stream to a higher level stream reader with the required encoding format. 
     StreamReader readStream = new StreamReader( ReceiveStream, encode );
     Console.WriteLine("\nResponse stream received");
     Char[] read = new Char[256];

        // Read 256 charcters at a time.    
     int count = readStream.Read( read, 0, 256 );
        Console.WriteLine("HTML...\r\n");

    while (count > 0) 
    {
            // Dump the 256 characters on a string and display the string onto the console.
        String str = new String(read, 0, count);
        Console.Write(str);
        count = readStream.Read(read, 0, 256);
    }

...

answered Jan 19, 2011 at 19:36

Aaron McIver

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1 Comment

Alexei Levenkov Over a year ago

RoR needs line-by-line reading - ReadLine of reader would work better for that case.

ajma · Accepted Answer · 2011-01-19 19:34:27Z

2

If you're reading text, try using a TextReader

WebRequest test = WebRequest.Create("http://www.domain.com/file.txt");
Stream something = test.GetRequestStream();
TextReader reader = (TextReader)new StreamReader(something);
string textfile = reader.ReadToEnd();

answered Jan 19, 2011 at 19:34

ajma

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1 Comment

Alexei Levenkov Over a year ago

+1 Ajma: no reason to cast StreamReader to TextReader as it is already TextReader. RoR: use ReadLine instead of ReadToEnd.

George Johnston · Accepted Answer · 2011-01-19 19:43:57Z

0

All a stream is, is a sequence of bytes. MemoryStreams, FileStream, etc. all inherit from System.IO.Stream

If you are simply attempting to compare the MD5 has against a local file, you could do something such as the following (not tested):

// Download File
WebClient wc = new WebClient();
byte[] bytes = wc.DownloadData();

MD5 md5 = System.Security.Cryptography.MD5.Create();
byte[] hash = md5.ComputeHash(bytes);

StringBuilder onlineFile = new StringBuilder();
for (int i = 0; i < hash.Length; i++)
{
   onlineFile.Append(hash[i].ToString("X2"));
}

// Load Local File
FileStream fs = new FileStream(@"c:\yourfile.txt",FileMode.Open);
byte[] fileBytes = new byte[fs.Length];
fs.Read(fileBytes, 0, fileBytes.Length);

byte[] hash = md5.ComputeHash(fileBytes);

StringBuilder localFile = new StringBuilder();
for (int i = 0; i < hash.Length; i++)
{
   onlineFile.Append(hash[i].ToString("X2"));
}


if(localFile.ToString() == onlineFile.ToString())
{
   // Match
}

edited Jan 19, 2011 at 19:43

answered Jan 19, 2011 at 19:34

George Johnston

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1 Comment

Alexei Levenkov Over a year ago

StreamReaders, StreamWriters do not inherit from Stream.

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