Make Disposable Module

Question

Hello,

I used this code but copied it into a module:

https://learn.microsoft.com/en-us/dotnet/visual-basic/programming-guide/language-features/strings/walkthrough-encrypting-and-decrypting-strings

No idea what's the difference if I copy it inside a module or class, however, I need to make it disposable, so I can use it by USING, what changes shall be made to get it disposable? Thanks for advise :)

Answer 1

Hi @Peter Volz ,

To make the class Simple3Des disposable you need to implement the IDisposable interface and then add the Dispose method to the class to release the resource. Since both TripleDESCryptoServiceProvider and SHA1CryptoServiceProvider classes implement the IDisposable interface, you need to make sure to call their Dispose method at the appropriate time to release related resources.

Public NotInheritable Class Simple3Des
    Implements IDisposable

    Private TripleDes As New TripleDESCryptoServiceProvider
    Private sha1 As New SHA1CryptoServiceProvider
    Private disposed As Boolean = False

    Private Function TruncateHash(ByVal key As String, ByVal length As Integer) As Byte()
        Dim keyBytes() As Byte = System.Text.Encoding.Unicode.GetBytes(key)
        Dim hash() As Byte = sha1.ComputeHash(keyBytes)
        ReDim Preserve hash(length - 1)
        Return hash
    End Function

    Sub New(ByVal key As String)
        TripleDes.Key = TruncateHash(key, TripleDes.KeySize \ 8)
        TripleDes.IV = TruncateHash("", TripleDes.BlockSize \ 8)
    End Sub

    Public Function EncryptData(ByVal plaintext As String) As String
        Dim plaintextBytes() As Byte = System.Text.Encoding.Unicode.GetBytes(plaintext)
        Dim ms As New System.IO.MemoryStream
        Dim encStream As New CryptoStream(ms, TripleDes.CreateEncryptor(), System.Security.Cryptography.CryptoStreamMode.Write)
        encStream.Write(plaintextBytes, 0, plaintextBytes.Length)
        encStream.FlushFinalBlock()
        Return Convert.ToBase64String(ms.ToArray)
    End Function

    Public Function DecryptData(ByVal encryptedtext As String) As String
        Dim encryptedBytes() As Byte = Convert.FromBase64String(encryptedtext)
        Dim ms As New System.IO.MemoryStream
        Dim decStream As New CryptoStream(ms, TripleDes.CreateDecryptor(), System.Security.Cryptography.CryptoStreamMode.Write)
        decStream.Write(encryptedBytes, 0, encryptedBytes.Length)
        decStream.FlushFinalBlock()
        Return System.Text.Encoding.Unicode.GetString(ms.ToArray)
    End Function

    Public Sub Dispose() Implements IDisposable.Dispose
        Dispose(True)
        GC.SuppressFinalize(Me)
    End Sub

    Protected Sub Dispose(disposing As Boolean)
        If Not disposed Then
            If disposing Then

                TripleDes.Dispose()
                sha1.Dispose()
            End If
            disposed = True
        End If
    End Sub

    Protected Overrides Sub Finalize()
        Dispose(False)
        MyBase.Finalize()
    End Sub
End Class

Then you can use the Using statement to ensure the correct release of resources.

Best Regards.

Jiachen Li

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Answer 2

if I copy it inside a module or

A VB modul is nothing OO related and so can't implement interfaces, nor can inherit and all the other OO stuff.

Use a class instead.