550 file unavailable error with FtpWebRequest class file upload. Works fine in FileZilla

Question

I'm searched and found other questions on this but none have solved my issues. I'm trying to upload a file via FTP using sample MSDN code. I get the The remote server returned an error: (550) File unavailable (e.g., file not found, no access) error on this line: ftpstream.Close();

    string inputfilepath = @"C:\DWF\test.txt";
    string ftpfilepath = "/abc/def/hij/klm/nop/test.txt";
    string ftphost = "my-ser-ver1:2121";
    //here correct hostname or IP of the ftp server to be given  

    string ftpfullpath = "ftp://" + ftphost + ftpfilepath;
    FtpWebRequest ftp = (FtpWebRequest)FtpWebRequest.Create(ftpfullpath);
    ftp.Credentials = new NetworkCredential("user", "pass");
    //userid and password for the ftp server to given  

    ftp.KeepAlive = true;
    ftp.UseBinary = true;

    ftp.Method = WebRequestMethods.Ftp.UploadFile;
    FileStream fs = File.OpenRead(inputfilepath);
    byte[] buffer = new byte[fs.Length];
    fs.Read(buffer, 0, buffer.Length);
    fs.Close();
    Stream ftpstream = ftp.GetRequestStream();
    ftpstream.Write(buffer, 0, buffer.Length);
    ftpstream.Close(); 

I have double checked the URI for blank spaces and there are none. I am able to complete this task using filezilla with the same user login. There is no oddball default directory that is already part of my URI. One thing for sure is that I am connecting to a unix server so maybe there is a setting I am missing?

Edit #1 (Added error log from System.Net)

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Received response [220 Oracle Content Services FTP Server ready.]

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Sending command [USER myuser]

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Received response [331 Password required for myuser.]

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Sending command [PASS ********]

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Received response [230 Login successful.]

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Sending command [OPTS utf8 on]

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Received response [500 Command not supported: OPTS]

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Sending command [PWD]

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Received response [257 "/"]

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Sending command [TYPE I]

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Received response [200 TYPE set to I.]

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Sending command [PASV]

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Received response [227 Entering Passive Mode (10,8,9,50,77,53)]

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Sending command [STOR abc/def/hij/klm/nop/test.txt]

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Received response [150 Ok to send data.]

System.Net Verbose: 0 : [7584] Exiting FtpWebRequest#10964107::GetRequestStream() 

System.Net Information: 0 : [7584] FtpControlStream#62182359 - Received response [550 Access denied.]

System.Net Information: 0 : [7584] FtpWebRequest#10964107::(Releasing FTP connection#62182359.)

Answer 1

This did the trick. apparently the CWD command behavior changed in the move from .NET 3.5 to 4.0.

You have to first call the method in this link.

http://support.microsoft.com/kb/2134299