VB.Net中的文件比较

发布时间：2020-12-17 07:23:15 所属栏目：百科来源：网络整理

导读：我需要知道两个文件是否相同.起初我比较了文件大小和创建时间戳,但这不够可靠.我已经提出了以下代码,这似乎有效,但我希望有人能够更好,更容易或更快地完成这项工作. 基本上我正在做的是将文件内容流式传输到字节数组,并通过System.Security.Cryptography比较

我需要知道两个文件是否相同.起初我比较了文件大小和创建时间戳,但这不够可靠.我已经提出了以下代码,这似乎有效,但我希望有人能够更好,更容易或更快地完成这项工作.

基本上我正在做的是将文件内容流式传输到字节数组,并通过System.Security.Cryptography比较它们的MD5哈希值.

在此之前,我做了一些简单的检查,因为没有理由读取文件,如果两个文件路径相同,或者其中一个文件不存在.

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

解决方法

我会说散列文件是要走的路,这就是我过去的做法.

在使用Streams等时使用Using语句,因为它们会自行清理.
这是一个例子.

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

（编辑：李大同）

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