Esteban Maldonado
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Esteban Maldonado's blog

Basic Async/Await in Unity C#!

Trying it out on Editor Windows

Esteban Maldonado's photo
Esteban Maldonado
Β·May 21, 2022Β·

5 min read

Basic Async/Await in Unity C#!

Photo by Ferenc Almasi on Unsplash

Table of contents

  • Context
  • Creating the Editor Window
  • Now Some Code Work!
  • Now The Fun Part!
  • What's going on?
  • Please let me know what you think!


I was a bit bored, and wanted to test regular C# asynchronous programming with Unity Editor Windows, that's it! 😁

For this post, I created a new Unity project with the latest 2021.3 LTS

Creating the Editor Window

If you don't have one, create a folder called Editor inside of the main Assets folder: image.png

Unity reacts differently to specific folder names, and it's best to store all custom editor UI scripts and assets on this folder: image.png

From Unity's Manual:

Editor scripts add functionality to Unity during development, but aren’t available in builds at runtime. Scripts in a Editor folder run as Editor scripts, not runtime scripts. You can have multiple Editor folders placed anywhere inside the Assets folder. Place your Editor scripts inside an Editor folder or a subfolder within it.

Since we're in version 2021.3, let's take advantage of Unity's new UI Toolkit package, which comes now pre-installed in the editor.

Inside of the Assets/Editor folder, let's create a new EditorWindow: image.png

This will bring in the following pop-up: image.png

Insert the name you'd like, and click on the Confirm button. You'll create these new files: image.png

Your new EditorWindow consists of 3 files:

  • UXML:
    From Unity's Manual:

    HTML and XML inspired markup language defines the structure of UI and reusable UI templates. Although you can build interfaces directly in C# files, Unity recommends using UXML documents if possible.

  • USS:
    From Unity's Manual:

    Style sheets apply visual styles and behaviors to UI. They’re similar to Cascading Style Sheets (CSS) used on the web, and support a subset of standard CSS properties. Although you can apply styles directly in C# files, Unity recommends using USS files if possible.

  • Editor Window C# script: This is the script that defines the logic of your editor window, whenever reacting to input events like button clicks, mouse moves, etc.

Double-click on the ThreadingTestWindow.uxml file: image.png

This will bring up the UI Builder: image.png

From there, let's add a new Button and change a few settings on it: Unity_ecd2FeOTwC.gif

  1. Add a button by dragging it from the component library
  2. Change the button's name to "doWorkButton"
  3. Change the button's text to "Do Work!"

Additionally, add a slider int to the window (trust me, we'll use it!): image.png

And let's change the name of the label to mainLabel image.png

Now Some Code Work!

Double-click on the ThreadingTestWindow .cs file to open the editor window script: image.png

Switch the code contents with the following:

using UnityEditor;
using UnityEngine;
using UnityEngine.UIElements;

using System.Threading;
using System.Threading.Tasks;

public class ThreadingTestWindow : EditorWindow
    [MenuItem("My Samples/ThreadingTestWindow")]
    public static void ShowExample()
        ThreadingTestWindow wnd = GetWindow<ThreadingTestWindow>();
        wnd.titleContent = new GUIContent("ThreadingTestWindow");

    private Button m_doWorkButton;
    private Label m_messageLabel;
    const int k_fakeDelayTimeInMS = 400;

    private void CreateGUI()



        m_messageLabel = rootVisualElement.Q<Label>("mainLabel");

    private void ImportUXML()
        var visualTree = AssetDatabase.LoadAssetAtPath<VisualTreeAsset>(
        VisualElement labelFromUXML = visualTree.Instantiate();

    private void PrepareAsynchronousWorkButton()
        m_doWorkButton = rootVisualElement.Q<Button>("doWorkButton");
        m_doWorkButton.clicked += OnDoWorkButtonClicked;

    async private void OnDoWorkButtonClicked()
        m_messageLabel.text = "";

        await ActualAsyncWork();

    async private Task ActualAsyncWork()
        string message = "ASYNC IS VERY COOL!";

        foreach(char messageChar in message)
            m_messageLabel.text += messageChar;
            await Task.Delay(k_fakeDelayTimeInMS);


    private void PrepareSynchronousWorkButton()
        var synchronousWorkButton = new Button(ActualSyncWork); = "doSynchronousWorkButton";
        synchronousWorkButton.text = "Do Work Synchronously!";

    private void ActualSyncWork()
        m_messageLabel.text = "";
        string message = "TOO SLOW!";

        foreach (char messageChar in message)
            m_messageLabel.text += messageChar;

Make sure to save the file, and then the editor will re-compile all scripts.

Let's now test our editor window! You'll be able to find the window under: image.png

Now The Fun Part!

When you have the editor window open, click on the synchronous work button: Unity_mZPiR242wy.gif

Look at how slow it is (on purpose though). The window is locked and you can't do anything else!

But look at what happens when we click on the button above: Unity_0RKn8fIwde.gif

It's still slow (also on purpose), but at least we can continue using the window! We can use this for segments of a window that require some time to execute a long operation.

What's going on?

Using C#'s built-in async and await keywords, we can unbind instructions from the UI's current execution.

Note: Using async and await does NOT necessarily mean that our code is being executed in a separate thread!

I went ahead and added this line of code when running either the asynchronous or the synchronous functions in the code:

Debug.Log($"Doing work on thread: {Thread.CurrentThread.ManagedThreadId}");

And at all times, I was using the same thread: image.png

And interestingly enough, under the hood the C# compiler turns your awaited code into an internal state machine, as discussed on Vasil Kosturski's cool articles on this matter. Which means that there's a high overhead cost to using these 2 keywords, and we should take this into account when applying it in our solutions.

For more information, definitely read the Microsoft's documentation on asynchronous programming. It uses a nice breakfast making analogy to explain the topic.

Please let me know what you think!

  • Did you know about async and await?
  • Have you used them for editor and/or run-time code in Unity C#?
  • Did you know about what happens under the hood when using these keywords?

πŸŽ‰πŸŽ‰πŸŽ‰Happy coding!!πŸŽ‰πŸŽ‰πŸŽ‰

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