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File Comparison in VB.Net

I need to know if two files are identical. At first I compared file sizes and creation timestamps, but this is not reliable enough. I came up with the following code that seems to work, but I hope someone has a better, easier, or faster way to do this.

Basically, what I'm doing is streaming the contents of the file to byte arrays and comparing their MD5 hashes with System.Security.Cryptography.

Before that, I do some simple checks because there is no reason to read files if both file paths are identical or one of the files does not exist.

Public Function CompareFiles(ByVal file1FullPath As String, ByVal file2FullPath As String) As Boolean

    If Not File.Exists(file1FullPath) Or Not File.Exists(file2FullPath) Then
        'One or both of the files does not exist.
        Return False
    End If

    If String.Compare(file1FullPath, file2FullPath, True) = 0 Then
        ' fileFullPath1 and fileFullPath2 points to the same file...
        Return True
    End If

    Dim MD5Crypto As New MD5CryptoServiceProvider()
    Dim textEncoding As New System.Text.ASCIIEncoding()

    Dim fileBytes1() As Byte, fileBytes2() As Byte
    Dim fileContents1, fileContents2 As String
    Dim streamReader As StreamReader = Nothing
    Dim fileStream As FileStream = Nothing
    Dim isIdentical As Boolean = False

    Try

        ' Read file 1 to byte array.
        fileStream = New FileStream(file1FullPath, FileMode.Open)
        streamReader = New StreamReader(fileStream)
        fileBytes1 = textEncoding.GetBytes(streamReader.ReadToEnd)
        fileContents1 = textEncoding.GetString(MD5Crypto.ComputeHash(fileBytes1))
        streamReader.Close()
        fileStream.Close()

        ' Read file 2 to byte array.
        fileStream = New FileStream(file2FullPath, FileMode.Open)
        streamReader = New StreamReader(fileStream)
        fileBytes2 = textEncoding.GetBytes(streamReader.ReadToEnd)
        fileContents2 = textEncoding.GetString(MD5Crypto.ComputeHash(fileBytes2))
        streamReader.Close()
        fileStream.Close()

        ' Compare byte array and return result.
        isIdentical = fileContents1 = fileContents2

    Catch ex As Exception

        isIdentical = False

    Finally

        If Not streamReader Is Nothing Then streamReader.Close()
        If Not fileStream Is Nothing Then fileStream.Close()
        fileBytes1 = Nothing
        fileBytes2 = Nothing

    End Try

    Return isIdentical
End Function
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2 answers

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Public Function CompareFiles(ByVal file1FullPath As String, ByVal file2FullPath As String) As Boolean

If Not File.Exists(file1FullPath) Or Not File.Exists(file2FullPath) Then
    'One or both of the files does not exist.
    Return False
End If

If file1FullPath = file2FullPath Then
    ' fileFullPath1 and fileFullPath2 points to the same file...
    Return True
End If

Try
    Dim file1Hash as String = hashFile(file1FullPath)
    Dim file2Hash as String = hashFile(file2FullPath)

    If file1Hash = file2Hash Then
        Return True
    Else
        Return False
    End If

Catch ex As Exception
    Return False
End Try
End Function

Private Function hashFile(ByVal filepath As String) As String
    Using reader As New System.IO.FileStream(filepath, IO.FileMode.Open, IO.FileAccess.Read)
        Using md5 As New System.Security.Cryptography.MD5CryptoServiceProvider
            Dim hash() As Byte = md5.ComputeHash(reader) 
            Return System.Text.Encoding.Unicode.GetString(hash) 
        End Using
    End Using
End Function
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