Assigning a reference type object a value on a secondary thread, and then working with this object from my primary thread - vb.net

Question

I am trying to create a variable which is of type MyReferenceTypeObject and of value null on thread one, use a delegate to make this thread equal to a new instance of MyReferenceTypeObject on thread two, and then access members of MyReferenceTypeObject back on thread one (in the delegates callback method).
My code is below:
Module Module1
Delegate Sub EditReferenceTypePropertyDelegate(ByVal referenceTypeObject As MyReferenceTypeObject, ByVal numberToChangeTo As Integer)
Sub Main()
Dim editReferenceDelegate = New EditReferenceTypePropertyDelegate(AddressOf EditReferenceTypeProperty)
Dim newReferenceTypeObject As MyReferenceTypeObject
editReferenceDelegate.BeginInvoke(newReferenceTypeObject, 2, AddressOf EditReferenceCallback, newReferenceTypeObject)
Console.ReadLine()
End Sub
Sub EditReferenceTypeProperty(ByVal referenceTypeObject As MyReferenceTypeObject, ByVal numberToChangeTo As Integer)
referenceTypeObject = New MyReferenceTypeObject()
referenceTypeObject.i = numberToChangeTo
End Sub
Sub EditReferenceCallback(ByVal e As IAsyncResult)
Dim referenceObject = DirectCast(e.AsyncState, MyReferenceTypeObject)
Console.WriteLine(referenceObject)
End Sub
End Module
Class MyReferenceTypeObject
Public Property i As Integer
End Class
However, newReferenceTypeObject comes into my callback method as null. I think I understand why, but the problem is that I need to pull some data from a database which I then need to pass into the constructor of newReferenceTypeObject, this takes a couple of seconds, and I don't want to lock up my UI while this is happening. I want to create a field of type MyReferenceTypeObject on thread one, instantiate this on thread two (after I have pulled the data of the database to pass into the constructor) and then work with members of the object back on thread one once the instantiation is complete.
Is this possible? I am using VB.Net with .Net 4.0 on Visual Studio 2012.

Answer 1

If you want to keep the GUI responsive during a long running action, I'd consider using the Task<> library (Comes with .NET 4.0). Here's a quick example.
Sub Main()
Dim instantiateTask = New Task(Of MyReferenceTypeObject)(Function()
' Call your database to pull the instantiation data.
Return New MyReferenceTypeObject With {.i = 2}
End Function)
instantiateTask.Start() ' Start the task -> invokes a ThreadPool.Thread to do the work.
instantiateTask.ContinueWith(Sub(x)
Console.WriteLine(x.Result.I)
End Sub, TaskScheduler.FromCurrentSynchronizationContext())
End Sub
.Wait blocks the GUI thread. However, you could use ContinueWith which is async and therefor nonblocking. Also you need to provide the TaskScheduler ( TaskScheduler.FromCurrentSynchronizationContext ) from the GUI thread to prevent cross-thread exceptions in case you want to update the UI from within the async method.