Visual Basic .NET Language Threading Performing thread-safe calls using Async/Await
Example
If we try to change an object on the UI thread from a different thread we will get a cross-thread operation exception:
Private Sub Button_Click(sender As Object, e As EventArgs) Handles MyButton.Click
' Cross thread-operation exception as the assignment is executed on a different thread
' from the UI one:
Task.Run(Sub() MyButton.Text = Thread.CurrentThread.ManagedThreadId)
End Sub
Before VB 14.0 and .NET 4.5 the solution was invoking the assignment on and object living on the UI thread:
Private Sub Button_Click(sender As Object, e As EventArgs) Handles MyButton.Click
' This will run the conde on the UI thread:
MyButton.Invoke(Sub() MyButton.Text = Thread.CurrentThread.ManagedThreadId)
End Sub
With VB 14.0, we can run a Task on a different thread and then have the context restored once the execution is complete and then perform the assignment with Async/Await:
Private Async Sub Button_Click(sender As Object, e As EventArgs) Handles MyButton.Click
' This will run the code on a different thread then the context is restored
' so the assignment happens on the UI thread:
MyButton.Text = Await Task.Run(Function() Thread.CurrentThread.ManagedThreadId)
End Sub
