Compare Files

This example illustrates how to compare two files.

Imports System.IO
Imports System.Security.Cryptography

Public Class Form1

Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

If CompareFiles("C:\Temp\2filecopy.bat", "C:\Temp\4filecopy.bat") = True Then
  MsgBox("The same")
Else
  MsgBox("Different")
End If

  End
End Sub

Public Function CompareFiles(ByVal FileFullPath1 As String, ByVal FileFullPath2 As String) As Boolean
'returns true if two files passed to is are identical, false otherwise
'does byte comparison; works for both text and binary files

'Throws exception on errors; you can change to just return 
'false if you prefer

Dim objMD5 As New MD5CryptoServiceProvider()
Dim objEncoding As New System.Text.ASCIIEncoding()
Dim aFile1() As Byte, aFile2() As Byte
Dim strContents1, strContents2 As String
Dim objReader As StreamReader
Dim objFS As FileStream
Dim bAns As Boolean

'If Not File.Exists(FileFullPath1) Then _
' Throw New Exception(FileFullPath1 & " doesn't exist")
'If Not File.Exists(FileFullPath2) Then _
' Throw New Exception(FileFullPath2 & " doesn't exist")

If Not File.Exists(FileFullPath1) Or Not File.Exists(FileFullPath2) Then
  Return False
  Exit Function
End If

Try
  objFS = New FileStream(FileFullPath1, FileMode.Open)
  objReader = New StreamReader(objFS)
  aFile1 = objEncoding.GetBytes(objReader.ReadToEnd)
  strContents1 = _
  objEncoding.GetString(objMD5.ComputeHash(aFile1))
  objReader.Close()
  objFS.Close()

  objFS = New FileStream(FileFullPath2, FileMode.Open)
  objReader = New StreamReader(objFS)
  aFile2 = objEncoding.GetBytes(objReader.ReadToEnd)
  strContents2 = _
  objEncoding.GetString(objMD5.ComputeHash(aFile2))

  bAns = strContents1 = strContents2
  objReader.Close()
  objFS.Close()
  aFile1 = Nothing
  aFile2 = Nothing

Catch ex As Exception
  Throw ex
End Try

Return bAns
End Function
End Class