Stream Reader And Buffer

[bennett]

I have written the following function

        Public Function ReadFile(ByVal FileName As String) As String
            Dim objReader As StreamReader = Nothing
            Dim objData As New StringBuilder
            Dim strReturn As String = ""
            Try
                objReader = New StreamReader(FileName, Encoding.Default, True, 512)
                objData.Append(objReader.ReadToEnd)
                strReturn = objData.ToString
            Catch Ex As Exception
                objReader.Dispose()
                strReturn = Ex.Message
            Finally
                objReader.Dispose()
            End Try
            Return strReturn
        End Function

When i am creating the streamreader I have specified of 512 (I presume thats bytes) for the buffer. Thats fine but i am also given the option when reading from the stream reader to .Read(Buffer,In dex, Count) what is the difference between the two buffer sizes?

Cheers