Object reference not set to an instance in p.start()

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I am using the below code to invoke exe which is there in the server. On p.start() ,console will open and close in 2 sec only. no exception is logging. exe is not getting executed.sometime i get "Object reference not set to an instance". what is the issue here?

MessageBox.Show("Excel Formatting started");
                     // Console.WriteLine("Formatting started " + DateTime.Now);

                      Process p = new Process();
                      p.StartInfo.UseShellExecute = false;
                      p.StartInfo.RedirectStandardOutput = true;
                      p.StartInfo.FileName = str_Automate_ExecleFormatExePath;
                      p.StartInfo.Arguments = '"' + strb_FilesList.ToString() + '"';
                      p.Start();

                      p.WaitForExit();

                      MessageBox.Show("Formatting completed");

What I have tried:

The same code is working fine in my local machine when exe and UI in local machine.
when i place exe in server and try to invoke from local UI, console will open and close without executing exe and no execptions logging.

Posted 31-Mar-20 4:10am

Member 14781099

Updated 31-Mar-20 4:31am

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Dave Kreskowiak 31-Mar-20 11:20am

Is this a web application (ASP.NET)?

Richard Deeming 1-Apr-20 13:22pm

If this is a web application or a Windows service, Office interop won't work:
Considerations for server-side Automation of Office[^]
Microsoft does not currently recommend, and does not support, Automation of Microsoft Office applications from any unattended, non-interactive client application or component (including ASP, ASP.NET, DCOM, and NT Services), because Office may exhibit unstable behavior and/or deadlock when Office is run in this environment.

If you're just launching an executable from a network share, it will be running on your computer, not on the server. You will need to have Office installed on the computer that launches the executable, and your user account will need to have suitable permissions on the share and any paths that executable uses.

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Richard MacCutchan · Answer 1 · 2020-03-31T04:21:00

Solution 1

C#

p.StartInfo.FileName = str_Automate_ExecleFormatExePath;
p.StartInfo.Arguments = '"' + strb_FilesList.ToString() + '"';

Add some print statements to show exactly what values are in these strings. It is most likely some missing information.

Posted 31-Mar-20 4:21am

Richard MacCutchan

OriginalGriff · Answer 2 · 2020-03-31T04:32:00

This is one of the most common problems we get asked, and it's also the one we are least equipped to answer, but you are most equipped to answer yourself.

Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable.
It's a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen. If you reach into the pocket and find there isn't a pen there, you can't sign your name on a piece of paper - and you will get very funny looks if you try! The empty pocket is giving you a null value (no pen here!) so you can't do anything that you would normally do once you retrieved your pen. Why is it empty? That's the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterdays shirt when you took it off last night.

We can't tell, because we weren't there, and even more importantly, we can't even see your shirt, much less what is in the pocket!

Back to computers, and you have done the same thing, somehow - and we can't see your code, much less run it and find out what contains null when it shouldn't.
But you can - and Visual Studio will help you here. Run your program in the debugger and when it fails, VS will show you the line it found the problem on. You can then start looking at the various parts of it to see what value is null and start looking back through your code to find out why. So put a breakpoint at the beginning of the method containing the error line, and run your program from the start again. This time, VS will stop before the error, and let you examine what is going on by stepping through the code looking at your values.

But we can't do that - we don't have your code, we don't know how to use it if we did have it, we don't have your data. So try it - and see how much information you can find out!