Outlook 2013 Add-In MailItem creation blocking Outlook

Question

I'm currently playing around with Office 2013 Add-Ins with Visual Studio 2013. I've created a Ribbon with a Button that displays a little Windows Form:

        private void outterMailCreateNewFaxBTN_Click(object sender, RibbonControlEventArgs e)
    {
        CreateNewFax cnf = new CreateNewFax(this);
        cnf.Show();
    }

When the user clicks on one of the buttons on the Form, a new MailItem is being created (with some information inside it).

private void button1_Click(object sender, EventArgs e)
    {
        this.Dispose();
        this.outterMailRibbon.setFaxNumber(faxNumber, this);
    }

Here is the setFaxNumber-Method:

public void setFaxNumber(String faxNumber, CreateNewFax cnf)
    {
        cnf = null;
        //mother.Dispose();
        this.faxNumber = faxNumber;

        Outlook.Application application = Globals.ThisAddIn.Application;
        Outlook.MailItem myMailItem = (Outlook.MailItem)application.CreateItem(Outlook.OlItemType.olMailItem);

        myMailItem.To = this.faxNumber;
        myMailItem.Subject = "[FAX:" + this.faxNumber + "]";
        myMailItem.BodyFormat = Outlook.OlBodyFormat.olFormatPlain;
        ((Outlook.ItemEvents_10_Event)myMailItem).Send += new Microsoft.Office.Interop.Outlook.ItemEvents_10_SendEventHandler(ThisAddIn_Send);
        this.gMailItem = myMailItem;
        myMailItem.Display(true);

    }

The problem im currently facing is that after the user clicked on the specific button on the Form the Outlook main-process is blocked and the UI freezes until the newly created Message is sent or discarded.

How can I avoid this behaviour (so that the user is able to display other Mails from outlook, while this newly created MailItem is still editable by the user)?

EDIT: The Outlook-UI freezes after the MailItem was created. At the Time, the Windows Form is still opened, Im able to use the Outlook-UI as usual.

Answer 1

EDIT:

Try changing myMailItem.Display(true); with myMailItem.Display(false); as the the MailItem.Display documentation states that false is the default modal parameter. If set to true outlook will freeze until its ready.

---

OLD ANSWER (In most UI freezing situations this will fix the problem, however this case was different) :

By going on what you have said it sounds like the send mail method is holding up the main thread until it is sent off, this will cause the main UI to freeze. The best way to deal with a freezing UI is to thread the method or sometimes you could use a dispatcher timer and put the method inside the tick.

I am not sure if this would work as I am writing from memory but if you were to thread the function you could do it like this:

    var thread = new Thread( () =>
    {
        this.outterMailRibbon.setFaxNumber(faxNumber, this);
    });

    thread.Start();
    thread.Join(); // The thread will auto leave and close once the execution is complete

The above code will execute the setFaxNumber method in a new thread separate from the main thread which the UI runs on, this means it will not hold up any UI loading.

If you need any more info just ask and I can add it to my answer :)