Lose UserProperties of TaskRequestItem when it is passed to Outlook Application (VSTO Addin)

Question

I create a TaskRequestItem via .NET Outlook Interop API and add my own UserProperty. (I use the already running Outlook instance) At the end I display the item in Outlook and the 1st process is over.

In my Outlook is running a VSTO Addin, which listen to the event ItemSend. If now I send the TaskRequestItem in Outlook, I cannot find in the Event ItemSend on the item any UserProperties!

I also tried with ItemProperties and the PropertyAccessor. Same problem, all properties have disappeared!

If I try this with a MailItem, then it works!

Adding the properties works first, because I can read them out right after adding them in 1st step...

Part 1 to create new item with interop api:

Microsoft.Office.Interop.Outlook.Application outlook = Marshal.GetActiveObject("Outlook.Application") as OutlookApplication;

...

TaskItem item = outlook.CreateItem(OlItemType.olTaskItem);
var task = item.Assign();
var guid = Guid.NewGuid().ToString();
var userProperty = item.UserProperties.Add("My GUID", OlUserPropertyType.olText, true);
userProperty.Value = guid;
task.Save();
task.Display();

...

Part 2 ItemSend in VSTO Addin

private void MyAddIn_ItemSend(object item, ref bool cancel)

...

var oItm = item as TaskRequestItem;
foreach (UserProperty property in oItm.UserProperties)
{
    if (property.Name == "My GUID")
    {
        Console.WriteLine("My GUID: " + property.Value);
    }
}

Dmitry Streblechenko Dmitry Streblechenko · Accepted Answer · 2019-10-23T15:05:51

The Task itself is never sent - it remains in the Tasks folder with all the user properties intact. What is sent is a TaskRequestItem object, which is distinct from the original lask object. You can call TaskRequestItem.GetAssociatedTask to retrieve the original Task object and copy your custom properties.

Lose UserProperties of TaskRequestItem when it is passed to Outlook Application (VSTO Addin)

1 Answers