Hacktoberfest 2026: the issues maintainers tagged for October, open and beginner-friendly. Browse Hacktoberfest issues

[Bug] RelayCommand Source Generator Fails Silently for Methods Starting With ‘On'

Open
  • Is something wrong?
#1,215 0 comments 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
68/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
csharp
Domain
tooling

Research direction

Start with the RelayCommand source generator and the name-handling path for methods beginning with On. Reproduce the issue using the provided TestViewModel and binding, then compare the generated property name with the documented behavior. Done means OnPointerPressed generates PointerPressedCommand and the Avalonia binding compiles.

Written by the indexing model from the issue text.

Description

bug :bug:
Describe the bug

Methods annotated with [RelayCommand] whose names start with On fail to generate command properties.

The documentation states that:

The name of the generated command will be created based on the method name. The generator will use the method name and append "Command" at the end, and it will strip the "On" prefix, if present. Additionally, for asynchronous methods, the "Async" suffix is also stripped before "Command" is appeneded.

However, the actual behaviour I am experiencing contradicts this claim.

Regression

No response

Steps to reproduce

Prerequisites:

  • .NET 10
  • C# 13
  1. Create a new Avalonia (Ver. 12.1.3) desktop project. Your project file should include:
<TargetFramework>net10.0</TargetFramework>
<RuntimeIdentifier>win-x64</RuntimeIdentifier>

  1. Add the CommunityToolkit.Mvvm (Ver. 8.4.2) NuGet package.

  2. Create a ViewModel with [RelayCommand] methods starting with On.

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using System.Diagnostics;

namespace MyTestApp.Avalonia.ViewModels;

public partial class TestViewModel : ObservableObject

(etc.)

	[RelayCommand]
	private void OnPointerPressed()
	{
		Debug.WriteLine("Pointer pressed.");
	}

	[RelayCommand]
	private void AsdfPointerPressed()
	{
		Debug.WriteLine("Pointer pressed.");
	}
  1. Create a TestView. Attempt to bind to OnPointerPressedCommand.
<Window
	x:Class="MyTestApp.Avalonia.Views.TestView"
	xmlns="https://github.com/avaloniaui"
	xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
	xmlns:vm="using:MyTestApp.Avalonia.ViewModels"
	Name="TestView"
	x:DataType="vm:TestViewModel">

    <!-- This binding will fail to compile. -->
    <Button Command="{Binding OnPointerPressedCommand}" />

    <!-- This binding will compile successfully. -->
    <Button Command="{Binding AsdfPointerPressedCommand}" />

</Window>
Expected behavior

In the ViewModel, [RelayCommand] private void OnPointerPressed() { } would generate a PointerPressedCommand property, which the View could then execute.

Screenshots

No response

IDE and version

VS 2022

IDE version

18.10.2

Nuget packages
  • CommunityToolkit.Common
  • CommunityToolkit.Diagnostics
  • CommunityToolkit.HighPerformance
  • CommunityToolkit.Mvvm (aka MVVM Toolkit)
Nuget package version(s)

8.4.2

Additional context

No response

Help us help you

No, just wanted to report this

Dominant language
C#
Stars
3.8k
Forks
400
No merged PRs in 30d

Getting set up

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from CommunityToolkit/dotnet

All issues in CommunityToolkit/dotnet

Similar issues

More C# issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.