使用F＃的Outlook互操作MailItem

Question

I am converting C# to F# for outlook email messages. This function will be called inside a try...with block if an exception occurs to email me. I normally use an SMTP mail service that works in the production environment only. I have to use Outlook in Dev.

open System.Net.Mail
open System.Runtime.InteropServices
open System.Reflection
open System.Collections
open System.Threading
open Microsoft.Office.Interop
open Microsoft.Office.Interop.Outlook

let sendEmail2 (sMessage:string) =
    let subject = "Load Failed at " + DateTime.Now.ToString() + "."
    let body = sMessage
    let app = new Outlook.ApplicationClass
    let mailItem = new app.CreateItem(OlItemType.olMailItem)
    //let mailItem = app.CreateItem(OlItemType.olMailItem)
    mailItem.Subject = subject
    mailItem.Body = body
    mailItem.To = "user@mycompany.com"
    mailItem.Send()

The issue is creating the MailItem. The original C# code did this

Outlook.Application app = new Outlook.Application();
Outlook.MailItem mailItem = app.CreateItem(Outlook.OlItemType.olMailItem);

I tried to use the C# code to the right of the equals sign, fully referencing the the interop assembly, etc. I even looked at an example from MSDN Word and Excel to reference the ApplicationClass. I even thought to use MailItemClass but, it is protected.

It always errors at the mailItem line with an error:

Incomplete structured construct at or before this point in expression

Answer 1

The error message indicates that there is a syntax error somewhere near the point where the error was reported. So, looking just at that, the first problem is that you are missing arguments when constructing an instance of Outlook.ApplicationClass . It should be:

let app = new Outlook.ApplicationClass()

As already mentioned in the comments, there are other issues - assignment should be written using <- and app.CreateItem is a method call, so you do not need new there:

let mailItem = app.CreateItem(OlItemType.olMailItem)
mailItem.Subject <- subject
mailItem.Body <- body
mailItem.To <- "user@mycompany.com"

As a side-note, this is probably not an area where you'd get a lot of benefits from using F#, so if this is for work, it might be better to leave the code in C# and use F# for some more functional problems than for Office interop. But you can certainly do this in F# too.