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Design:
After browse the file using fileUpload, there is one button onClick event followed. In that event, am upload the file which is in fileUpload to the driveHq.com ftp server.


Problem:
* Object reference not set to an instance of an object

Why its happening?

Note:
* User credentials are checked clearly
* Also checked, am still free member for this account and having free space for storing data.


CODE:

try
          {
                FileUpload1.SaveAs(Server.MapPath("~/Upload/") + FileUpload1.FileName);

                FtpWebRequest myFtpWebRequest;
                FtpWebResponse myFtpWebResponse;
                StreamWriter myStreamWriter;
                NetworkCredential myNetworkCredential;
                StreamWriter myStream;
                StreamReader myReadStream;                        
                
                myFtpWebRequest = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://ftp.drivehq.com/" + FileUpload1.FileName));
                myNetworkCredential = new NetworkCredential();
                myNetworkCredential.UserName = txtfldUsername.Text;
                myNetworkCredential.Password = txtfldPassword.Text;
                myFtpWebRequest.Credentials = myNetworkCredential;
                myFtpWebRequest.Method = WebRequestMethods.Ftp.UploadFile;
                myFtpWebRequest.UseBinary = true;

                myStream = new StreamWriter(myFtpWebRequest.GetRequestStream());// This line causes problem
                myStreamWriter = myStream;
                myReadStream = new StreamReader(Server.MapPath("~/Upload/") + FileUpload1.FileName);
                myStreamWriter.Write(myReadStream.ReadToEnd());
                myStreamWriter.Close();
                myReadStream.Close();

                myFtpWebResponse = (FtpWebResponse)myFtpWebRequest.GetResponse();
                //Label6.Text = myFtpWebResponse.StatusDescription;
                myFtpWebResponse.Close();
                LblStatus.Text = "Status : File uploaded successfully";               
            }
            catch (Exception ex)
            {
                LblStatus.Text = "Status : "+ ex.Message;
            }
Posted
Updated 5-Apr-15 9:09am
v2
Comments
F-ES Sitecore 5-Apr-15 15:10pm
   
What line gives you the null reference error?
Md Sadham 6-Apr-15 2:55am
   
Please see thee code which have comment text like this:
// This line causes problem.
I found that problem by using break point and debugger. Am cannot find out which member having null. However, i replaced by another code and its solved the problem. THanks!

1 solution

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Solution 1

You did not show where the exception with the message "Object reference not set to an instance of an object" is thrown.

Not to worry. This is one of the very easiest cases to detect and fix. It simply means that some member/variable of some reference type is dereferenced by using and of its instance (non-static) members, which requires this member/variable to be non-null, but in fact it appears to be null. Simply execute it under debugger, it will stop the execution where the exception is thrown. Put a break point on that line, restart the application and come to this point again. Evaluate all references involved in next line and see which one is null while it needs to be not null. After you figure this out, fix the code: either make sure the member/variable is properly initialized to a non-null reference, or check it for null and, in case of null, do something else.

Please see also: want to display next record on button click. but got an error in if condition of next record function "object reference not set to an instance of an object".

Sometimes, you cannot do it under debugger, by one or another reason. One really nasty case is when the problem is only manifested if software is built when debug information is not available. In this case, you have to use the harder way. First, you need to make sure that you never block propagation of exceptions by handling them silently (this is a crime of developers against themselves, yet very usual). The you need to catch absolutely all exceptions on the very top stack frame of each thread. You can do it if you handle the exceptions of the type System.Exception. In the handler, you need to log all the exception information, especially the System.Exception.StackTrace:
http://msdn.microsoft.com/en-us/library/system.exception.aspx,
http://msdn.microsoft.com/en-us/library/system.exception.stacktrace.aspx.

The stack trace is just a string showing the full path of exception propagation from the throw statement to the handler. By reading it, you can always find ends. For logging, it's the best (in most cases) to use the class System.Diagnostics.EventLog:
http://msdn.microsoft.com/en-us/library/system.diagnostics.eventlog.aspx.

Good luck,
—SA
   

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