主题：[求助]这个接口怎么写？详情见下【暂时没问题】快递鸟api

Class SurroundingClass

    Private Function base64(ByVal str As String, ByVal charset As String) As String

        Return Convert.ToBase64String(System.Text.Encoding.GetEncoding(charset).GetBytes(str))

    End Function

    Private Function encrypt(ByVal content As String, ByVal keyValue As String, ByVal charset As String) As String

        If keyValue IsNot Nothing Then

            Return base64(MD5(content + keyValue, charset), charset)

        End If

        Return base64(MD5(content, charset), charset)

    End Function

End Class

这样写对吗？