mvvm

mvvm is a skill for Claude Code, Codex from managedcode/dotnet-skills. It costs 120 tokens per session (2,392 once invoked), scanned A, original, MIT.

A guide to Model-View-ViewModel (MVVM), a way to separate a .NET app's user interface from its data and interaction logic.

In plain words
What is it for?
Use it to structure .NET interfaces, connect screens to data with binding, implement commands and state changes, and test ViewModels without opening the UI.
Why use it?
It makes UI code easier to test and maintain by keeping screen behavior in ViewModels instead of mixing it into the visual layer.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/managedcode/dotnet-skills/mvvm
Any agent
npx skills add managedcode/dotnet-skills --skill mvvm
Clone the repo
git clone --depth 1 https://github.com/managedcode/dotnet-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for mvvm

README.md
[![agentmods](https://agentmods.dev/badge/skills/managedcode/dotnet-skills/mvvm.svg)](https://agentmods.dev/skills/managedcode/dotnet-skills/mvvm)
Your own site
<a href="https://agentmods.dev/skills/managedcode/dotnet-skills/mvvm"><img src="https://agentmods.dev/badge/skills/managedcode/dotnet-skills/mvvm.svg" alt="Measured on agentmods" height="20"></a>
Per session 120 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,392 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00120 $0.02392
Opus 5 $0.00060 $0.01196
Sonnet 5 $0.00024 $0.00478
Haiku 4.5 $0.00012 $0.00239

Measured 2d ago against content hash c2ef7dacf119, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

mvvm scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

catalog/Libraries/MVVM-Toolkit/skills/mvvm/SKILL.md · 378 lines

How it starts

The opening of the file, as written. The whole thing — 378 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MVVM Pattern for .NET

Trigger On

  • implementing UI separation with Model-View-ViewModel
  • using MVVM Toolkit (CommunityToolkit.Mvvm) for ViewModels
  • designing testable UI architecture
  • handling commands, property changes, and messaging
  • choosing between MVVM frameworks

Documentation

References

See detailed examples in the references/ folder:

Core Concepts

Component Responsibility Example
Model Business logic and data Product, Order, User
View UI presentation (XAML/Razor) ProductPage.xaml
ViewModel UI logic and state ProductViewModel

Workflow

  1. Keep Views dumb — no business logic in code-behind
  2. Use data binding — connect View to ViewModel properties
  3. Commands for actions — handle user interactions via ICommand
  4. Inject dependencies — services go into ViewModel constructors
  5. Test ViewModels — they should be unit testable without UI

MVVM Toolkit Setup

<PackageReference Include="CommunityToolkit.Mvvm" Version="8.*" />

ViewModel Patterns

Basic ViewModel with Source Generators

public partial class ProductViewModel(IProductService productService) : ObservableObject
{
    [ObservableProperty]
    private string _name = string.Empty;

    [ObservableProperty]
    private decimal _price;

    [ObservableProperty]
    [NotifyCanExecuteChangedFor(nameof(SaveCommand))]
    private bool _isValid;

    [RelayCommand(CanExecute = nameof(CanSave))]
    private async Task SaveAsync()
    {
        await productService.SaveAsync(new Product { Name = Name, Price = Price });
    }

    private bool CanSave() => IsValid && !string.IsNullOrEmpty(Name);
}

Read the full file on GitHub · 378 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 378 lines · 120 tokens per session scan A c2ef7dacf119

Subscribe to this mod's changes

mvvm is a skill published in the GitHub repository managedcode/dotnet-skills (477 stars, last pushed yesterday), licensed MIT. It adds 120 tokens to every session and 2,392 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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