What I learned today... (SMTP via VB.NET, Singleton class instance)

Well, the first thing I learned was more about COM Interop. Boy, is that cool stuff for legacy applications and working with VBA!

At work we use BusinessObjects and publish reports through its Broadcast Agent, which is a tool for scheduling reports to be run and publishing to the BusinessObjects Web Intelligence ASP application. The "full client" has VBA macro capabilities supported by a complete BusinessObjects object model. With that being said, I have created a piece of macro code to automate the publishing process and email the report, either in the standard BO report form, PDF, or Excel XLS spreadsheet format. The class below is the email component. The original came from somewhere here on the web... When I find the original author, I'll update this posting.

Imports System.Web.Mail
Imports Microsoft.VisualBasic.Compatibility.VB6

Namespace Mail
    Public Class SMTP
        Private mTo As String
        Private mFrom As String
        Private mSubject As String
        Private mMessage As String
        Private mAttachments As New Collection
        Private mServer As String = "localhost"

        Public Sub New()
            ' Needed for COM Interop.
            ' Do not remove.
            ' Nothing to see here, move along...
        End Sub

        Public Property [To]() As String
            Get
                Return mTo
            End Get
            Set(ByVal Value As String)
                mTo = Value
            End Set
        End Property

        Public Property From() As String
            Get
                Return mFrom
            End Get
            Set(ByVal Value As String)
                mFrom = Value
            End Set
        End Property

        Public Property Subject() As String
            Get
                Return mSubject
            End Get
            Set(ByVal Value As String)
                mSubject = Value
            End Set
        End Property

        Public Property Message() As String
            Get
                Return mMessage
            End Get
            Set(ByVal Value As String)
                mMessage = Value
            End Set
        End Property

        Public Property Attachments() As Collection
            Get
                Return mAttachments
            End Get
            Set(ByVal Value As Collection)
                mAttachments = Value
            End Set
        End Property

        Public Property Server() As String
            Get
                Return mServer
            End Get
            Set(ByVal Value As String)
                mServer = Value
            End Set
        End Property

        Public Sub Send()
            Try
                Dim mail As New MailMessage
                With mail
                    .From = Trim(Me.From)
                    .To = Trim(Me.To)
                    .Subject = Trim(Me.Subject)
                    .Body = Trim(Me.Message)
                    If Me.Attachments.Count > 0 Then
                        Dim file As String
                        For Each file In mAttachments
                            .Attachments.Add(New MailAttachment(Trim(file)))
                        Next
                    End If
                End With

                SMTPMail.SmtpServer = mServer

                SMTPMail.Send(mail)

            Catch ex As Exception
                Throw New System.Exception(ex.Message, CType(ex, System.Exception))
            End Try
        End Sub

    End Class
End Namespace

Some notes about this code:

1. Since this is a COM Interop class, a few things are needed.
   1. Microsoft.VisualBasic.Compatibility.VB6
      : This has the classic Collections object in it. If you aren't using COM, this can easily be replaced with an ArrayList.
   2. A New method. This is the default constructor that COM needs. You can initialize any default values in here, but in this case all I needed was an empty contructor.
2. The To property takes a comma delimited list of email addresses.
3. The attachment collection needs to be a colelction of strings. These strings would be the file names with path.

Pretty cool, huh?

The other thing I learned was the use of Shared (VB.NET) and static (C#). I found out how to create a Singleton instance of a class and use it correctly (I think)...

Here's a VB.NET sample:

Namespace SingletonExample
    Friend Class SingletonClass
        Private Shared mSingletonClass As SingletonClass = Nothing

        Public Shared ReadOnly Property SingletonClass() As SingletonClass
            Get
                If mSingletonClass Is Nothing Then
                    mSingletonClass = New SingletonClass
                End If

                Return mSingletonClass
            End Get
        End Property

        Shared Sub New()
            ' Nothing to see here, keep moving...
        End Sub

        Public Shared Sub Initialize()
            Console.WriteLine("In SingletonExample.SingletonClass")
        End Sub
    End Class
End Namespace

To call this, simply use the following:

SingletonExample.SingletonClass.Initialize()

I'm not totally clear yet on how this exactly works, but I'm a lot closer and can implement this methodology in my apps.

Looks like I'm a little more learned in .NET!