Advanced Overview

This section covers advanced extension development topics for developers who want to build sophisticated Visual Studio integrations.

What You’ll Learn

Topic	Description
MEF Components	Editor extensions using Managed Extensibility Framework
Language Services	IntelliSense, syntax highlighting, and code navigation
Debugger Integration	Custom debug engines and visualizers
Source Control	Version control provider integration
Project Types	Custom project systems
Performance	Optimization techniques and best practices

Prerequisites

Before diving into advanced topics, ensure you’re comfortable with:

• Service Provider patterns
• Packages and registration
• Commands and UI
• Async Services and threading

Advanced Architecture

MEF (Managed Extensibility Framework)

MEF is used extensively in the VS editor for composition:

[Export(typeof(IWpfTextViewCreationListener))]
[ContentType("CSharp")]
[TextViewRole(PredefinedTextViewRoles.Editable)]
internal sealed class MyEditorExtension : IWpfTextViewCreationListener
{
    [Import]
    internal IClassificationTypeRegistryService ClassificationRegistry { get; set; }

    public void TextViewCreated(IWpfTextView textView)
    {
        // Extension is automatically instantiated by MEF
    }
}

Language Service Protocol (LSP)

Modern language services can use LSP for cross-editor compatibility:

[Export(typeof(ILanguageClient))]
[ContentType("myLanguage")]
public class MyLanguageClient : ILanguageClient
{
    public string Name => "My Language Server";

    public async Task<Connection> ActivateAsync(CancellationToken token)
    {
        var process = StartLanguageServer();
        return new Connection(process.StandardOutput.BaseStream,
                             process.StandardInput.BaseStream);
    }
}

Visual Studio SDK Interop

Advanced scenarios often require direct COM interop:

// Get the running object table
IVsRunningDocumentTable rdt = await VS.Services.GetRunningDocumentTableAsync();

// Enumerate open documents
rdt.GetRunningDocumentsEnum(out IEnumRunningDocuments enumDocs);
uint[] cookies = new uint[1];
while (enumDocs.Next(1, cookies, out uint fetched) == VSConstants.S_OK && fetched == 1)
{
    rdt.GetDocumentInfo(cookies[0], out uint flags, out uint readLocks,
        out uint editLocks, out string moniker, out IVsHierarchy hierarchy,
        out uint itemId, out IntPtr docData);
}

Common Advanced Patterns

Deferred Initialization

Load expensive components only when needed:

public class MyService : IMyService
{
    private readonly Lazy<ExpensiveComponent> _component;

    public MyService()
    {
        _component = new Lazy<ExpensiveComponent>(() =>
        {
            // Only created on first access
            return new ExpensiveComponent();
        });
    }

    public void DoWork()
    {
        _component.Value.Process();
    }
}

Weak Event Handlers

Prevent memory leaks with weak events:

public class MyComponent
{
    private readonly ITextBuffer _buffer;

    public MyComponent(ITextBuffer buffer)
    {
        _buffer = buffer;
        // Use weak event manager
        WeakEventManager<ITextBuffer, TextContentChangedEventArgs>
            .AddHandler(buffer, nameof(ITextBuffer.Changed), OnBufferChanged);
    }

    private void OnBufferChanged(object sender, TextContentChangedEventArgs e)
    {
        // Handle change
    }
}

Solution Load Events

React to solution lifecycle:

VS.Events.SolutionEvents.OnAfterOpenSolution += OnSolutionOpened;
VS.Events.SolutionEvents.OnBeforeCloseSolution += OnSolutionClosing;
VS.Events.SolutionEvents.OnAfterOpenProject += OnProjectOpened;

private void OnSolutionOpened(Solution solution)
{
    // Initialize solution-specific features
}

Debugging Advanced Extensions

Diagnostic Logging

Add detailed logging for troubleshooting:

private static readonly TraceSource _trace = new TraceSource("MyExtension");

public async Task DoWorkAsync()
{
    _trace.TraceEvent(TraceEventType.Information, 0, "Starting work...");
    try
    {
        await PerformWorkAsync();
        _trace.TraceEvent(TraceEventType.Information, 0, "Work completed.");
    }
    catch (Exception ex)
    {
        _trace.TraceEvent(TraceEventType.Error, 0, $"Error: {ex}");
        throw;
    }
}

Performance Profiling

Use VS’s built-in profiling:

// Mark performance-sensitive regions
using (var marker = new PerformanceMarker("MyOperation"))
{
    // Code to measure
}

Getting Help

For advanced scenarios:

• Visual Studio SDK Documentation
• VS Extensibility GitHub
• VSSDK Extensibility Samples

Next Steps

Start with MEF Components to learn about editor extensibility through composition.