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Update AV1835: Beware of async/await deadlocks in UI frameworks (e.g. WPF, WinForms) #378

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dennisdoomen merged 1 commit into from
Mar 29, 2026
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Update AV1835: Beware of async/await deadlocks in UI frameworks (e.g. WPF, WinForms) #378

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4 changes: 2 additions & 2 deletions _rules/1835.md
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
---
rule_id: 1835
rule_category: performance
title: Beware of `async`/`await` deadlocks in special environments (e.g. WPF)
title: Beware of `async`/`await` deadlocks in UI frameworks (e.g. WPF, WinForms)
severity: 1
---
Consider the following asynchronous method:
Expand All @@ -20,4 +20,4 @@ Now when a button event handler is implemented like this:
textBox1.Text = data;
}

You will likely end up with a deadlock. Why? Because the `Result` property getter will block until the `async` operation has completed, but since an `async` method _could_ automatically marshal the result back to the original thread (depending on the current `SynchronizationContext` or `TaskScheduler`) and WPF uses a single-threaded synchronization context, they'll be waiting on each other. A similar problem can also happen on UWP, WinForms, classical ASP.NET (not ASP.NET Core) or a Windows Store C#/XAML app. Read more about this [here](https://devblogs.microsoft.com/pfxteam/await-and-ui-and-deadlocks-oh-my/).
You will likely end up with a deadlock. Why? Because the `Result` property getter will block until the `async` operation has completed, but since an `async` method _could_ automatically marshal the result back to the original thread (depending on the current `SynchronizationContext` or `TaskScheduler`) and WPF uses a single-threaded synchronization context, they'll be waiting on each other. A similar problem can also happen on WinForms. Read more about this [here](https://devblogs.microsoft.com/pfxteam/await-and-ui-and-deadlocks-oh-my/).