VB.NET stream read calculate crc32 - vb.net

Question

I am reading files using stream reader and writer with a buffer. Is it possible to calculate the crc32 checksum of the file at the same time so that it would evaluate the buffer during each iteration, and the result would be the crc32 of the complete file, instead of having to read teh file twice? Here is the code:
Public Function APPEND_FILE_TO_FILE(ByVal SOURCE_FILE As String, ByVal DESTINATION_FILE As String)
Dim nn As New FileInfo(SOURCE_FILE)
Dim BUFFER(BUFFER_SIZE) As Byte
Dim BYTES_READ As Long = 0
Using inFile As New System.IO.FileStream(SOURCE_FILE, IO.FileMode.Open, IO.FileAccess.Read)
Using outFile As New System.IO.FileStream(DESTINATION_FILE, IO.FileMode.OpenOrCreate, IO.FileAccess.Write)
Do
BYTES_READ = inFile.Read(BUFFER, 0, BUFFER_SIZE)
TOTAL_PROCESSED_DATA += BYTES_READ ' GUI related
outFile.Write(BUFFER, 0, BYTES_READ)
Loop While BYTES_READ > 0
End Using
End Using
End Function
CRC32 function:
Public Function GetCRC32(ByVal sFileName As String) As String
Try
Dim FS As FileStream = New FileStream(sFileName, FileMode.Open, FileAccess.Read, FileShare.Read, 8192)
Dim CRC32Result As Integer = &HFFFFFFFF
Dim Buffer(4096) As Byte
Dim ReadSize As Integer = 4096
Dim Count As Integer = FS.Read(Buffer, 0, ReadSize)
Dim CRC32Table(256) As Integer
Dim DWPolynomial As Integer = &HEDB88320
Dim DWCRC As Integer
Dim i As Integer, j As Integer, n As Integer
'Create CRC32 Table
For i = 0 To 255
DWCRC = i
For j = 8 To 1 Step -1
If (DWCRC And 1) Then
DWCRC = ((DWCRC And &HFFFFFFFE) \ 2&) And &H7FFFFFFF
DWCRC = DWCRC Xor DWPolynomial
Else
DWCRC = ((DWCRC And &HFFFFFFFE) \ 2&) And &H7FFFFFFF
End If
Next j
CRC32Table(i) = DWCRC
Next i
'Calcualting CRC32 Hash
Do While (Count > 0)
For i = 0 To Count - 1
n = (CRC32Result And &HFF) Xor Buffer(i)
CRC32Result = ((CRC32Result And &HFFFFFF00) \ &H100) And &HFFFFFF
CRC32Result = CRC32Result Xor CRC32Table(n)
Next i
Count = FS.Read(Buffer, 0, ReadSize)
Loop
Return Hex(Not (CRC32Result))
Catch ex As Exception
Return ""
End Try
End Function

Answer 1

The above code leaves the file being parsed [open] and cannot be renamed or deleted.
The line:
Count = FS.Read(Buffer, 0, ReadSize)
Loop
Return Hex(Not (CRC32Result))
Should Be:
Count = FS.Read(Buffer, 0, ReadSize)
Loop
FS.Close
Return Hex(Not (CRC32Result))
Then the file can be manipulated again.