Delaying the use of code while a file is created? - vb.net

Question

Okay, so my program is checking to see is a textfile exist (this works) then if it doesn't exist it's creating the directory and file as well as saving the data to the file. I receive the error when it drops into the second test statement to create the text file.
The program will create the directory and file, but fail to write to it. "unhandeled exception: file is being used by another process. If I click to ignore the error and run the program, I can click the save button again and it works properly.
So I guess my question is, can I somehow delay the code that writes to the file long enough for the other operation to finish, or is there a better way to structure it, so it's not an issue.
Relevant Code:
Private Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click
'create necessary directory
'create text file
'if file exist write to file
If My.Computer.FileSystem.FileExists("C:\Documents and Settings\All Users\Documents\NailPolishSelector\polishColors.txt") = True Then
MsgBox("Data Saved")
Using sr As New IO.StreamWriter("C:\Documents and Settings\All Users\Documents\NailPolishSelector\polishColors.txt")
For Each line In lstColors.Items
sr.WriteLine(line)
Next
sr.Close()
End Using
ElseIf My.Computer.FileSystem.FileExists("C:\Documents and Settings\All Users\Documents\NailPolishSelector\polishColors.txt") = False Then
My.Computer.FileSystem.CreateDirectory("C:\Documents and Settings\All Users\Documents\NailPolishSelector")
Dim fs As FileStream = File.Create("C:\Documents and Settings\All Users\Documents\NailPolishSelector\polishColors.txt")
'error occurs here
Using srr As New IO.StreamWriter("C:\Documents and Settings\All Users\Documents\NailPolishSelector\polishColors.txt")
For Each line In lstColors.Items
srr.WriteLine(line)
Next
srr.Close()
End Using
MsgBox("File Created")
End If
End Sub

Answer 1

Your problem is that the file is locked by the fs FileStream object, and so the srr StreamWriter cannot write to it as it is trying to get a reference to the file by its name
So replacing
Using srr As New IO.StreamWriter("C:\Documents and Settings\All Users\Documents\NailPolishSelector\polishColors.txt")
with
Using srr As New IO.StreamWriter(fs)
should fix your problem.

Answer 2

Your code can be re-written somewhat to make it simpler and more robust. I'm guessing that if the file exists then you want to replace it, but if not then please remove the 'OPTIONAL piece of code:
Private Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click
' Get the All Users documents folder
Dim docsFolder As String = Environment.GetFolderPath(Environment.SpecialFolder.CommonDocuments)
' Combine it with the desired directory and filename
Dim theFile As String = Path.Combine(docsFolder, "NailPolishSelector\polishColors.txt")
'OPTIONAL
' Remove the previous version of the file
If My.Computer.FileSystem.FileExists(theFile) Then
File.Delete(theFile)
End If
' REQUIRED: Create the directory if it doesn't exist
If Not Directory.Exists(Path.GetDirectoryName(theFile)) Then
Directory.CreateDirectory(Path.GetDirectoryName(theFile))
End If
' Create the data file
File.AppendAllLines(theFile, lstColors.items)
MsgBox("Data saved.")
End Sub
(Thanks go to Magnus for pointing out File.AppendAllLines(path, lstColors.Items).)
There are a couple of things there which you may which to look up in the documentation: the use of the SpecialFolders enumeration and Path.Combine.