问.NET标准中未定义System.Security.Cryptography.MACTripleDES()

EN

Imports System.Security.Cryptography  

Shared Function Encode(ByVal value As String, _
                       ByVal key As String) As String
    Dim mac3des As New System.Security.Cryptography.MACTripleDES()
    Dim md5 As New System.Security.Cryptography.MD5CryptoServiceProvider()
    mac3des.Key = md5.ComputeHash(System.Text.Encoding.UTF8.GetBytes(key))
    Return Convert.ToBase64String( _
      System.Text.Encoding.UTF8.GetBytes(value)) & "-"c & _
      Convert.ToBase64String(mac3des.ComputeHash( _
      System.Text.Encoding.UTF8.GetBytes(value)))
End Function