Question

Hi I am Reading a file from the user’s computer then using specific network credentials to write it out to a network share this corrupts a very small percentage of the files.
when i open the files in a hex editor the hex is different on the first line

Header:    00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
Good File: 50 4b 03 04 14 00 08 00 00 00 37 57 51 41 6f 61
Bad File:  50 4b 03 04 14 00 08 00 00 00 b7 56 51 41 6f 61

The difference in columns 0a and 0b exist throughout the whole file,

If I am going about this the wrong way by all means correct me or if it is just something small that would be better. Any help is much appreciated. The code I am using is below

var fileStream = 
    new FileStream(source, FileMode.Open, FileAccess.Read, FileShare.None);

var impersonationContext =
    new WrapperImpersonationContext("myDomain", "myname", "myPass");

        impersonationContext.Enter();

        try
        {
            using (Stream file = File.OpenWrite(destination))
            {
                fileStream.CopyTo(file);
            }
        }
        catch (Exception e)
        {
            MessageBox.Show(e.Message);
        }
        finally
        {
            impersonationContext.Leave();

            if(fileStream != null)
            {
                fileStream.Close();
            }
        }

Answer 1

FileStream.CopyTo() will write n bytes into the destination file, but won’t erase the end of the destination file that previously existed. Opening the output stream with FileMode.Create should guarantee an exact copy.

Calling file.SetLength(file.Position); at the end may also work, but I’m not sure how reliably…