Cannot write to a file after reading it with IO.StreamReader - vb.net

Question

I am making an encryption program that also functions as a notepad (CryptoMatic). There is a Open function with the following code:
Dim r As New StreamReader(filename)
Dim text As String = r.ReadToEnd
txtFileContents.text = text
r.Dispose()
r.Close()
Now there is the save and save as button
the save button checks if the file had been saved previously or not. If yes then I am trying to write to that file with the following code:
Dim myFileStream As New System.IO.FileStream(filename, FileMode.Append, FileAccess.Write, FileShare.None)
myFileStream.Lock(0, 100)
Dim myWriter As New System.IO.StreamWriter(myFileStream)
myWriter.WriteLine(text)
myWriter.Flush()
myWriter.Close()
myFileStream.Close()
myFileStream.Unlock(0, 100)
Now when i press the save button it gives the following error:
The process cannot access the file 'C:\Users\VisualTech\Documents\Visual Studio 2010\Projects\CryptoMatic Update\CryptoMatic Update\bin\Debug\text.txt' because it is being used by another process.
and the application stops, can anyone please help me?

Answer 1

I have tried your code above and have noticed two things:
You don't need a myFileStream.Lock call because you already open it
with FileShare.None
You can't call myFileStream.Unlock(0, 100) after the call to
myFileStream.Close()
So I have rewritten your code in this way.
Sub Main
Dim text = "This is a text to write in the stream"
Using myFileStream As New System.IO.FileStream("D:\temp\testlock.txt", FileMode.Append, FileAccess.Write, FileShare.None)
Using myWriter As New System.IO.StreamWriter(myFileStream)
myWriter.WriteLine(text)
End Using
End Using
End Sub