A WinUI 3 question about accessing the UI thread from another thread, say, a Timer tick.
In WinForms that was extremely easy with a (someControl).InvokeRequired and .Invoke. In WPF we had to add .Dispatcher. and in UWP we had to specify a specific dispatcher: Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(...). But it still all worked just fine.
When I port my UWP solution (an extremely simple program to just show the issue), and adjust the name of the class (and thus its constructor), it still builds fine, but when I run it, I get an "a method was called at an unexpected time" exception. (Again: works fine as a UWP app)
I'll include my test code below:
Any idea what's happening here? HOW do I fix this, and, bonus answer: why does this happen in WinUI 3 and not in UWP?
(And yes, I'm aware of DispatcherTimer, I use Timer to demonstrate my problem: in my actual app I use something far more complicated than a timer, and I wanted to keep the demo code as concise and short as possible).
Demo code:
using Microsoft.UI.Xaml;
using System;
using System.Threading;
using Windows.UI.Core;
namespace WinUI3NotOwner
{
public sealed partial class MainWindow : Window
{
public Timer timer;
public int counter = 0;
public MainWindow()
{
this.InitializeComponent();
timer = new Timer(TimerTick, null, 1000, 1000);
}
public void TimerTick(Object stateInfo)
{
if (++counter == 3)
{
Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.Normal,
() => { TbTest.Text = "Works!"; }); // WinUI 3 code. Ignore the warning: we actually DON'T want to wait for its completion!
}
}
}
}
XAML code used:
<Window
x:Class="WinUI3NotOwner.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:WinUI3NotOwner"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">
<Grid>
<TextBox x:Name="TbTest" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="50,50,0,0" TextWrapping="Wrap" Text="TextBox" Width="200" Height="40"/>
</Grid>
</Window>
