FtpWebResponse and StreamReader - specifying an offset

Posted by AJ on Stack Overflow See other posts from Stack Overflow or by AJ
Published on 2010-04-22T08:01:50Z Indexed on 2010/04/22 8:03 UTC
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Hi,

I am using the FtpWebRequest / FtpWebResponse objects in C# to download files from a server - so far, so good. I create a StreamReader object from the response stream and use a StreamWriter to create a local file.

Now, the file I am reading happens to be in a very simple 'archive' format - there is a small TOC at the start of the file followed by the actual file data. I can therefore read the TOC and get a file offset and size of the data I want to download.

My question is: Supposing the offset is 1024. I would use StreamReader.Read(buffer, 1024, length), but will .NET and the FTP protocol actually allow me to skip bytes 0-1023, or does the reader still go through the (relatively) slow process of downloading and discarding the bytes I don't need? This may make the difference between whether I want to use a single archive file, or a TOC file with the data files stored separately.

As a bit of a secondary question, would my mileage vary using the Http classes instead of Ftp?

Cheers, Adam

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