VB - Writing to a file, closing and Object existance - vb.net

Question

I am writing a program that writes data to a text file at different points in my code, for example in different subroutines, functions or at different parts of subroutines (being scattered around).
First, I Dim the file writer:
Dim CurrentHisWriter As System.IO.StreamWriter
I tell it where to write to:
CurrentHisWriter = New System.IO.StreamWriter("C:\ProgramData\Japanese Conjugation Helper\LastSearch.txt")
Then, I actually write things:
CurrentHisWriter.Writeline("thing to write")
The problem is that I have to change to a different subroutine and then keep on writing to a file, so I have to close the writer and then dim another one in another subroutine:
CurrentHisWriter.Close
NewSubroutine()
[NewSubroutine]:
Dim CurrentHisWriter As System.IO.StreamWriter
CurrentHisWriter = New System.IO.StreamWriter("C:\ProgramData\Japanese Conjugation Helper\LastSearch.txt")
But then when I do this, I gives me one of a couple errors:
The program is has an instance of the file running
Some thing to do with there being no object (I don't remember exactly)
What is a reliable way programming the writing to files without having to worry about closing the writer at every point I change subroutines. I'm not sure about how objects and instances work and so the only thing I can do now is make a catch loop around every single line that uses the "CurrentHisWriter.Writeline" but this isn't really working too.
I know my lack of knowledge in this doesn't help explain, but I tried my best.

Answer 1

The naive approach would be like:
Sub Main()
MethodA()
MethodB()
End Sub
Sub MethodA()
Log("Starting method A")
End Sub
Sub MethodB()
Log("Starting method B")
End Sub
Sub Log(message as String)
System.IO.File.AppendAllText("C:\temp\my.log", message)
End Sub
File.AppendAllText is pretty good at closing things off so you can subsequently write to it elsewhere
A better approach would be to have a class whose job it is to build this file, and it builds it all into a stringbuilder and then writes it once. Multiple of your methods use that class, build that file... The class can either implement some timed/periodic dumping of data to disk (if it's like logging, never ending, thousands of events per second.. but then perhaps you'd just use a logging framework rather than reinvent the wheel), or it has a write method that saves the rendering of it to disk
If there is another specialized application of your data at work here, for example if you're generating XML or JSON you should look at specific serialization approaches for those (wheels that have already been invented)

Answer 2

I use
FileOpen(1, "file.txt", OpenMode.Append)
Now you can write from any other subroutine
PrintLine(1, "text to write")
Until the file is closed
FileClose(1)
But maybe you could solve your problem this way:
Define CurrentHisWriter outside of subroutine as
Private CurrentHisWriter As System.IO.StreamWriter = ....
Then you won't have to close and reopen the writer, all your Subs and functions will have access to it.