Question

I have a requirement where I need to convert .NET 4.0 project to .NET 3.5 project,
Everything else is fine except the “SmtpClient”
So far, I have found that .NET 3.5 SmtpClient does not implement IDisposable, while in .NET 4.0 it does!

Below is the code which works fine on .NET4.0 but not on .NET3.5:

Using MailServer As New SmtpClient(MailServerName)
MailServer.Credentials = New System.Net.NetworkCredential(MailServerUserName, MailServerPassword)
SendMail(MailServer, msgBody, msgSubject, FromEmail, ToEmail)
End Using

Any idea how to do it using .NET 3.5 (I prefer to use “Using” code block to auto dispose the object & not the old style manual dispose)

Answer 1

How about a TryCast to IDisposable before the Using:

Dim MailServer As New SmtpClient(MailServerName)
Using TryCast(MailServer, IDisposable)
    MailServer.Credentials = New System.Net.NetworkCredential(MailServerUserName, MailServerPassword)
    SendMail(MailServer, msgBody, msgSubject, FromEmail, ToEmail)
End Using

If running in .NET 4.0, the TryCast() returns the SmtpClient because it implements IDisposable.

If running in .NET 3.5, the TryCast() returns Nothing and the Using is ignored.

There does not appear to be any cleanup required for SmtpClient in .NET 3.5, since they didn’t provide a Dispose() or any other cleanup method as far as I can tell.