Write a file from Powershell then read it from C#

Question

I am invoking Powershell from C# to gather some information and using Out-File to send it to a text file. Then I need to read the lines from said file and do stuff with the data inside of C#.

string MyCommand = "-Command &{ get-process | Out-File C:\\MyFile.txt}";

ProcessStartInfo MyProcInfo = new ProcessStartInfo();
MyProcInfo.FileName = "powershell.exe";
MyProcInfo.Arguments = MyCommand;

Process MyProcess = new Process();
MyProcess.StartInfo = MyProcInfo;
MyProcess.Start();
MyProcess.WaitForExit();

try
{
  var lines = File.ReadLines(@"C:\MyFile.txt");
  (etc)
} 
catch (Exception Ex)
{
  MessageBox.Show(Ex.ToString());
}

So when it tries to open the text file I am getting a

"File Not Found"

exception. The file IS being written every time, so I am assuming that there is a timing thing going on which is why I am using WaitForExit. But it is still not able to 'find' the file.

Are you sure you have write access to C: and the file is written? Because of the UnauthorizedAccessException that is thrown when writing directly to C:, I doubt it. Use MyProcInfo.UseShellExecute = false; MyProcInfo.RedirectStandardOutput = true;, then redirect that output to a string and see where the problem is. while(!MyProcess.StandardOutput.EndOfStream) that encloses MyProcess.StandardOutput.ReadLine(); should do the trick. — jAC
– jAC, Commented Jul 18, 2017 at 21:10
Please note: The Powershell side IS working. The file does get written...I actually manually delete it each time to test. So I do have write access to C:\. I am getting problems when I get to File.ReadLines. That is when I get File Not Found — PSNewb
– PSNewb, Commented Jul 18, 2017 at 21:13
@wOxxOm You should actually use single-quote string literals if you don't plan on doing substitution. — Maximilian Burszley
– Maximilian Burszley, Commented Jul 18, 2017 at 21:50
I agree with @JanesAbouChleih. Your code gives me the same exception unless I write/read to/from a subdirectory (C:\temp\MyFile.txt). You say the file gets written but I'm skeptical because your code works as is for me with the exception of the file path. — Mufaka
– Mufaka, Commented Jul 18, 2017 at 21:58
Did you check the C:\ and see that the file was actually there? Windows does automatic folder re-direction and your C:\ write may have been redirected to %localappdata%\VirtualStore. If the file is there when viewed from explorer, what are the file permissions on the file? — Scott Chamberlain
– Scott Chamberlain, Commented Jul 18, 2017 at 21:59

Maximilian Burszley · Accepted Answer · 2017-07-18 21:54:33Z

1

Why don't you write the file with C# instead of PowerShell?

You can leverage the Diagnostics.Process .NET class (here's a PowerShell example)

$proc = [Diagnostics.Process]::Start($exe, $arguments)
$proc.WaitForExit()

answered Jul 18, 2017 at 21:54

Maximilian Burszley

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2 Comments

PSNewb Over a year ago

There's a lot more going on than what is listed in the powershell line I have here. I truncated it for the sake of brevity. But it is being written correctly every time it runs.

D.J. Over a year ago

You can call powershell inproc and use the output directly without the need to write it onto filesystem and read it again. Look at "stackoverflow.com/questions/16398171/…" for example

John · Accepted Answer · 2017-07-19 05:24:39Z

I can't tell you what is wrong but I can give you some tips to troubleshoot.

After MyProcess.WaitForExit() add a test for the file's existence.

if (File.Exists(@"C:\Myfile.txt"))
{
    ... file process code here....
}

Get rid of the hardcoded file names and use variables instead.

string filename = @"C:\MyFile.txt";

string MyCommand = "-Command &{ get-process | Out-File " & filename & "}";

then when you want to access the file use:

if (File.Exists(filename))
{
   ...process the file.
}

The advantage of this is that you are 100% guaranteed that you are using exactly the same filename in all places.

Add a breakpoint after MyProcess.WaitForExit(); Then, when the execution stops, navigate to the file and ensure that it is physically there AT THAT TIME and ensure that it is not locked by the program. For example, try to rename it or delete it. If it is still locked you should not be able to do either of those things. Also, most current versions of Windows have someplace that you can check for open files. If you tell me what OS you are running I might be able to tell you how to check that.

One more thing: another poster mentioned Windows Redirection. I personally have never had that happen when the file was explicitly fully qualified.

HTH, John

Vitaly · Accepted Answer · 2017-07-19 11:08:06Z

Hello!

You can try to do something like this:

maybe it help for you

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {

string MyCommand = "-Command &{ if (!(Test-Path 'c:\\test')) {md 'c:\\test'; get-process | Out-File c:\\test\\MyFile.txt}}";

ProcessStartInfo MyProcInfo = new ProcessStartInfo();
MyProcInfo.FileName = "powershell.exe";
MyProcInfo.Arguments = MyCommand;

Process MyProcess = new Process();
MyProcess.StartInfo = MyProcInfo;
MyProcess.Start();
MyProcess.WaitForExit();

try
{
    var lines = File.ReadLines(@"c:\test\MyFile.txt");
 foreach (var ln in lines) {
     Console.WriteLine(ln);
     Console.ReadKey();

 }
} 
catch (Exception Ex)
{
  Console.WriteLine(Ex.ToString());
  Console.ReadKey();
}
        }

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