VB Question

[crokett]

I think I need a good programming forum. I'm frustrated. Anyhoo, given this code:

Dim outLogPath As String = "C:\logfile.txt"
 Dim outLogStream As System.IO.StreamWriter

 If Not IO.File.Exists(outLogPath) Then
                    outDataStream = System.IO.File.CreateText(outLogPath)
                Else : outLogStream = New System.IO.StreamWriter(outLogPath, False)
                End If
 outLogStream.WriteLine("Log File Created")

The file gets created but doesn't get written to.
What am I missing?

[tjmac44]

I think I need a good programming forum. I'm frustrated. Anyhoo, given this code:

Dim outLogPath As String = "C:\logfile.txt"
 Dim outLogStream As System.IO.StreamWriter

 If Not IO.File.Exists(outLogPath) Then
                    outDataStream = System.IO.File.CreateText(outLogPath)
                Else : outLogStream = New System.IO.StreamWriter(outLogPath, False)
                End If
 outLogStream.WriteLine("Log File Created")

The file gets created but doesn't get written to.
What am I missing?

I am a Java guy, but if I read this correctly the very first time you run this, or the file C:\logfile.txt does not exists, the program will create a file called logfile.txt, but it will not create the object outLogStream. Does this throw a runtime exception when outLogStream is referenced after the "End if" without having been created with the New keyword?

What happens if you run this 2 times in a row?

I dont know the VB good enough to help you out much more.

[tjmac44]

I think I need a good programming forum. I'm frustrated. Anyhoo, given this code:

Dim outLogPath As String = "C:\logfile.txt"
 Dim outLogStream As System.IO.StreamWriter

 If Not IO.File.Exists(outLogPath) Then
                    outDataStream = System.IO.File.CreateText(outLogPath)
                Else : outLogStream = New System.IO.StreamWriter(outLogPath, False)
                End If
 outLogStream.WriteLine("Log File Created")

The file gets created but doesn't get written to.
What am I missing?

Not having a VB compiler, try something like this:

Dim outLogPath As String = "C:\logfile.txt"
Dim outLogStream As System.IO.StreamWriter

If Not IO.File.Exists(outLogPath) Then
outDataStream = System.IO.File.CreateText(outLogPath)
End If
outLogStream = New System.IO.StreamWriter(outLogPath, False)
outLogStream.WriteLine("Log File Created")

[Hoakie]

I am assuming you are trying to create the log file if it doesn't exist and append to it if it does. What you didn't do was call the Close method on the StreamWriter class.

Here is a cleaned up version of your code that works for me

Dim outLogPath As String = "C:\logfile.txt"
Dim outLogStream As System.IO.StreamWriter

If Not IO.File.Exists(outLogPath) Then
outLogStream = New System.IO.StreamWriter(outLogPath)
Else
outLogStream = New System.IO.StreamWriter(outLogPath, True)
End If
outLogStream.WriteLine("Log File Created")
outLogStream.Close()

[crokett]

Thanks John. I tried that using the close() function. It worked but then of course the code threw an exception the next time I tried to write to the file in the code. I need to write to the file while the program is running. It seems messy to close() and then repopen the stream every time I want to write a line. I tried using Flush() and that didn't work.

[Hoakie]

the alternative is to open the stream when the app opens, write to it throughout then close the stream when the app exits. However, the stream functions are pretty efficient so I would think for logging it would be better to open/close each time. This would insure you have captured all your log data and not lose it if the app crashes.

my 2cents

[Alex Franke]

This is how I would do it:

System.IO.File.AppendAllText( @"C:\logfile.txt", "Log file created.\r\n" );

This will create the file if it doesn't already exist, open the file, append the string to the end, and close the file -- everything you need it to do.

If you really really want to do it the hard way, you need to flush the stream, then close it. Also a file stream is a precious resource, so you don't want to keep an open handle to it any longer than you need to. Wrap the code in a "using" statement so the object will get explicitly finalized.

Just open/write/close -- there's nothing wrong with that. It's really the safest and cleanest way to do it.

If you're writing out a lot to a log file and you find that it is bogging down resources (test it first to be sure it actually is), then you have a couple of options: (1) Keep the filestream open, or (2) collect all the data you want to write it all at the same time at the end. The drawback of option 1 is that you're hanging on to system resources -- and it might not really benefit you that much, and the drawback of option 2 is that if your app crashes, you could lose a lot of log entries.

[Alex Franke]

Whoops -- that was in C#. Here it is in VB. It's just different syntax.

System.IO.File.AppendAllText( "C:\logfile.txt", "Log file created." + Environment.NewLine )

[crokett]

Thanks Alex, that is a great suggestion and I will do that.