Mvvm Toolkit Messenger

What it does

When your agent uses it

• Tasks that involve Event-driven systems

Example prompts

• “/mvvm-toolkit-messenger”

Workflow steps

6 steps, taken from the first numbered list in SKILL.md.

1. 1Capturing this in the lambda. (r, m) => OnX(m) implicitly
2. 2Strong-ref recipients without Unregister. With
3. 3Inherited message types. A handler registered for BaseMessage is
4. 4Wrong messenger instance. Sending via WeakReferenceMessenger.Default
5. 5OnActivated never runs. ObservableRecipient only registers
6. 6Cross-thread updates. The messenger is thread-agnostic. If a

What it can do on your machine

Read from SKILL.md and the folder at commit 727ff2e. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  No scripts in the folder and no shell commands in SKILL.md (its code samples are csharp).

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • learn.microsoft.com
  • github.com

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Mvvm Toolkit Messenger loads about 2.2k tokens when it runs, and up to ~4k if it reads all its reference files. Until then it costs about 108 tokens; SKILL.md has 573 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~108

When it runs · the whole SKILL.md, loaded when a task matches

~2.2k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~4k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from github/awesome-copilot at commit 727ff2e, republished under its MIT licence (© github). 573 words, ~2,214 tokens.

name

mvvm-toolkit-messenger

description

CommunityToolkit.Mvvm Messenger pub/sub for decoupled communication between ViewModels (or any objects). Covers WeakReferenceMessenger vs StrongReferenceMessenger, IRecipient<TMessage>, RequestMessage<T> / AsyncRequestMessage<T> / CollectionRequestMessage<T>, ValueChangedMessage<T>, channels (tokens), and the ObservableRecipient activation lifecycle. Use across WPF, WinUI 3, .NET MAUI, Uno, and Avalonia.

using CommunityToolkit.Mvvm.Messaging.Messages;

// Single-payload broadcast
public sealed class LoggedInUserChangedMessage(User user)
    : ValueChangedMessage<User>(user);

// Custom shape (records are great for this)
public sealed record ThemeChangedMessage(AppTheme NewTheme);

// Empty signal
public sealed record RefreshRequestedMessage;

WeakReferenceMessenger.Default.Register<MyViewModel, ThemeChangedMessage>(
    this,
    static (recipient, message) => recipient.OnThemeChanged(message.NewTheme));

public sealed class MyViewModel : ObservableRecipient,
    IRecipient<ThemeChangedMessage>,
    IRecipient<RefreshRequestedMessage>
{
    public void Receive(ThemeChangedMessage message) { /* ... */ }
    public void Receive(RefreshRequestedMessage message) { /* ... */ }
}

WeakReferenceMessenger.Default.RegisterAll(this);

WeakReferenceMessenger.Default.Send(new ThemeChangedMessage(AppTheme.Dark));

// Empty payloads use the parameterless overload:
WeakReferenceMessenger.Default.Send<RefreshRequestedMessage>();

const int LeftPaneChannel = 1;

WeakReferenceMessenger.Default.Register<MyViewModel, RefreshRequestedMessage, int>(
    this, LeftPaneChannel,
    static (r, _) => r.RefreshLeft());

WeakReferenceMessenger.Default.Send(new RefreshRequestedMessage(), LeftPaneChannel);

public sealed class CurrentUserRequest : RequestMessage<User> { }

WeakReferenceMessenger.Default.Register<UserService, CurrentUserRequest>(
    this,
    static (r, m) => m.Reply(r.CurrentUser));

User user = WeakReferenceMessenger.Default.Send<CurrentUserRequest>();

var request = WeakReferenceMessenger.Default.Send<CurrentUserRequest>();
if (request.HasReceivedResponse)
    User user = request.Response;

public sealed class CurrentUserRequest : AsyncRequestMessage<User> { }

WeakReferenceMessenger.Default.Register<UserService, CurrentUserRequest>(
    this,
    static (r, m) => m.Reply(r.GetCurrentUserAsync()));

User user = await WeakReferenceMessenger.Default.Send<CurrentUserRequest>();

public sealed class OpenDocumentsRequest : CollectionRequestMessage<Document> { }

var docs = WeakReferenceMessenger.Default.Send<OpenDocumentsRequest>();
foreach (Document doc in docs) { /* ... */ }

WeakReferenceMessenger.Default.Unregister<ThemeChangedMessage>(this);
WeakReferenceMessenger.Default.Unregister<ThemeChangedMessage, int>(this, LeftPaneChannel);
WeakReferenceMessenger.Default.UnregisterAll(this);

protected override void OnNavigatedTo(NavigationEventArgs e)
{
    base.OnNavigatedTo(e);
    ViewModel.IsActive = true;
}

protected override void OnNavigatedFrom(NavigationEventArgs e)
{
    ViewModel.IsActive = false;
    base.OnNavigatedFrom(e);
}

services.AddSingleton<IMessenger>(WeakReferenceMessenger.Default); // app-wide
services.AddScoped<WindowScopedMessenger>();                       // per-window

public sealed partial class WindowViewModel(IMessenger messenger)
    : ObservableRecipient(messenger) { }

© github, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 1 other file (references) in skills/mvvm-toolkit-messenger of github/awesome-copilot.

• SKILL.md
• references/messenger-patterns.md

Open the folder on GitHubat commit 727ff2e

Used in 1 other repository

We found 1 copy of this SKILL.md (exact, near-identical or edited) in other folders, from 1 other GitHub owner. This page covers the copy in github/awesome-copilot, which our catalogue first saw on October 7, 2026.

• boshi-xixixi/TraeSkill.trae/Skills/.agents/skills/mvvm-toolkit-messenger