title: Preserving existing text when writing to file
body: <p>In <code>Tester.txt</code> it simply says "Hello".</p>
  
  <p>I now run this:</p>
  
  <pre><code>Sub Main()
      Dim fileName As String
      Dim aFileStream As FileStream
      Dim aWriter As StreamWriter
      fileName = "...\Tester.txt"
      Try
          aFileStream = New FileStream(fileName, FileMode.OpenOrCreate)
          aWriter = New StreamWriter(aFileStream)
          aWriter.WriteLine("World")
      Catch ex As Exception
          MessageBox.Show("found this {0}", ex.Message)
      Finally
          If aWriter IsNot Nothing Then
              aWriter.Close()
          End If
          If aFileStream IsNot Nothing Then
              aFileStream.Close()
          End If
      End Try
  
  End Sub
  </code></pre>
  
  <p>Now "Hello" has been over-written with "World".</p>
  
  <p>I'd like to preserve the existing text in the file so I thought I could read that text into a variable first and then write the new stuff:</p>
  
  <pre><code>Sub Main()
      Dim fileName As String
      Dim aFileStream As FileStream
      Dim aWriter As StreamWriter
      Dim aReader As StreamReader
      fileName = "...\Tester.txt"
      Try
          aFileStream = New FileStream(fileName, FileMode.OpenOrCreate)
  
          aReader = New StreamReader(aFileStream)
          Dim myContent As String = aReader.ReadToEnd()
  
          aWriter = New StreamWriter(aFileStream)
          aWriter.WriteLine("World")
  
      Catch ex As Exception
          MessageBox.Show("found this {0}", ex.Message)
      Finally
          If aWriter IsNot Nothing Then
              aWriter.Close()
          End If
          If aReader IsNot Nothing Then
              aReader.Close()
          End If
          If aFileStream IsNot Nothing Then
              aFileStream.Close()
          End If
      End Try
  
  End Sub
  </code></pre>
  
  <p>Is this the standard way of preserving the text already in the file?<br>
  Can I preserve the existing information without using an instance of <code>StreamReader</code>  ?</p>