dotnet-xml-docs

XML documentation comments for .NET: all standard tags (<summary>, <param>, <returns>, <exception>, <remarks>, <example>, <value>, <typeparam>, <typeparamref>, <paramref>), advanced tags (<inheritdoc> for interface and base class inheritance, <see cref="..."/>, <seealso>, <c> and <code>), enabling XML doc generation with <GenerateDocumentationFile> MSBuild property, warning suppression strategies for internal APIs (CS1591, <NoWarn>, InternalsVisibleTo), XML doc conventions for public NuGet libraries, auto-generation tooling (IDE quick-fix /// trigger, GhostDoc-style patterns), and IntelliSense integration showing XML docs in IDE tooltips and autocomplete.

Version assumptions: .NET 8.0+ baseline. XML documentation comments are a C# language feature available in all .NET versions. <GenerateDocumentationFile> MSBuild property works with .NET SDK 6+. <inheritdoc> fully supported since C# 9.0 / .NET 5+.

Scope boundary: This skill owns XML documentation comment authoring -- the syntax, conventions, and MSBuild configuration for generating XML doc files. API documentation site generation from XML comments (DocFX, Starlight) is owned by [skill:dotnet-api-docs]. General C# coding conventions (naming, formatting) are owned by [skill:dotnet-csharp-coding-standards].

Out of scope: API documentation site generation from XML comments (DocFX setup, OpenAPI-as-docs, doc-code sync) -- see [skill:dotnet-api-docs]. General C# coding conventions and naming standards -- see [skill:dotnet-csharp-coding-standards]. CI/CD deployment of documentation sites -- see [skill:dotnet-gha-deploy].

Cross-references: [skill:dotnet-api-docs] for downstream API documentation generation from XML comments, [skill:dotnet-csharp-coding-standards] for general C# coding conventions, [skill:dotnet-gha-deploy] for doc site deployment.

Enabling XML Documentation Generation

MSBuild Configuration

Enable XML documentation file generation in the project or Directory.Build.props:

<!-- In .csproj or Directory.Build.props -->
<PropertyGroup>
  <GenerateDocumentationFile>true</GenerateDocumentationFile>
</PropertyGroup>

This generates a .xml file alongside the assembly during build (e.g., MyLibrary.xml next to MyLibrary.dll). NuGet pack automatically includes this XML file in the package, enabling IntelliSense for package consumers.

Warning Suppression for Internal APIs

When GenerateDocumentationFile is enabled, the compiler emits CS1591 warnings for all public members missing XML doc comments. Suppress warnings selectively for internal-facing code:

Option 1: Suppress globally for the entire project (not recommended for public libraries):

<PropertyGroup>
  <NoWarn>$(NoWarn);CS1591</NoWarn>
</PropertyGroup>

Option 2: Suppress per-file with pragma directives (recommended for mixed-visibility assemblies):

#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
public class InternalServiceHelper
{
    // This type is internal-facing despite being public
    // (e.g., exposed for testing via InternalsVisibleTo)
}
#pragma warning restore CS1591

Option 3: Use InternalsVisibleTo and keep internal types truly internal:

// In AssemblyInfo.cs or a Properties file
[assembly: InternalsVisibleTo("MyLibrary.Tests")]

// Mark internal-facing types as internal instead of public
internal class ServiceHelper
{
    // No CS1591 warning -- internal types are not documented
}

Option 4: Treat missing docs as errors for public libraries (strictest):

<PropertyGroup>
  <GenerateDocumentationFile>true</GenerateDocumentationFile>
  <!-- Treat missing XML docs as build errors -->
  <WarningsAsErrors>$(WarningsAsErrors);CS1591</WarningsAsErrors>
</PropertyGroup>

This forces documentation for every public member. Use this for NuGet packages where consumers depend on IntelliSense documentation.

Standard XML Doc Tags

<summary>

Describes the type or member. This is the primary tag that appears in IntelliSense tooltips.

/// <summary>
/// Provides methods for managing widgets in the system.
/// Widget operations are thread-safe and support cancellation.
/// </summary>
public class WidgetService
{
}

<param>

Documents a method parameter.

/// <summary>
/// Creates a new widget with the specified name and optional category.
/// </summary>
/// <param name="name">The display name for the widget. Must not be null or whitespace.</param>
/// <param name="category">
/// The category to assign. When <see langword="null"/>, the default category is used.
/// </param>
/// <param name="cancellationToken">A token to cancel the asynchronous operation.</param>
public async Task<Widget> CreateWidgetAsync(
    string name,
    string? category = null,
    CancellationToken cancellationToken = default)
{
}

<returns>

Documents the return value.

/// <summary>
/// Finds a widget by its unique identifier.
/// </summary>
/// <param name="id">The unique identifier of the widget.</param>
/// <returns>
/// The widget if found; otherwise, <see langword="null"/>.
/// </returns>
public async Task<Widget?> FindByIdAsync(Guid id)
{
}

<exception>

Documents exceptions that may be thrown.

/// <summary>
/// Updates the widget's name.
/// </summary>
/// <param name="id">The widget identifier.</param>
/// <param name="newName">The new name to assign.</param>
/// <exception cref="ArgumentException">
/// Thrown when <paramref name="newName"/> is null or whitespace.
/// </exception>
/// <exception cref="KeyNotFoundException">
/// Thrown when no widget with the specified <paramref name="id"/> exists.
/// </exception>
/// <exception cref="InvalidOperationException">
/// Thrown when the widget is in a read-only state and cannot be modified.
/// </exception>
public async Task UpdateNameAsync(Guid id, string newName)
{
}

<remarks>

Provides additional context beyond the summary. Use for implementation notes, usage guidance, and caveats.

/// <summary>
/// Computes the hash of the widget's content for change detection.
/// </summary>
/// <remarks>
/// <para>
/// The hash is computed using SHA-256 over the UTF-8 encoded content.
/// Results are deterministic across platforms and .NET versions.
/// </para>
/// <para>
/// This method is thread-safe. The returned hash is a lowercase hex string
/// without any prefix (e.g., "a1b2c3..." not "0xa1b2c3...").
/// </para>
/// </remarks>
/// <returns>A 64-character lowercase hexadecimal hash string.</returns>
public string ComputeContentHash()
{
}

<example>

Provides a code example demonstrating usage. Essential for public library APIs.

/// <summary>
/// Creates a new widget and persists it to the repository.
/// </summary>
/// <example>
/// <code>
/// var service = new WidgetService(repository, logger);
///
/// var widget = await service.CreateWidgetAsync(
///     "Dashboard Widget",
///     category: "Analytics",
///     cancellationToken: ct);
///
/// Console.WriteLine($"Created widget: {widget.Id}");
/// </code>
/// </example>
public async Task<Widget> CreateWidgetAsync(
    string name,
    string? category = null,
    CancellationToken cancellationToken = default)
{
}

<value>

Documents a property's value. Similar to <returns> but for properties.

/// <summary>
/// Gets the current status of the widget.
/// </summary>
/// <value>
/// The widget status. Defaults to <see cref="WidgetStatus.Draft"/> for new widgets.
/// </value>
public WidgetStatus Status { get; private set; }

<typeparam>

Documents a generic type parameter.

/// <summary>
/// A repository that provides CRUD operations for entities.
/// </summary>
/// <typeparam name="TEntity">
/// The entity type. Must implement <see cref="IEntity"/> and have a parameterless constructor.
/// </typeparam>
/// <typeparam name="TKey">
/// The type of the entity's primary key. Typically <see cref="Guid"/> or <see cref="int"/>.
/// </typeparam>
public interface IRepository<TEntity, TKey>
    where TEntity : class, IEntity
    where TKey : struct
{
}

Advanced Tags

<inheritdoc>

Inherits documentation from a base class or interface. Eliminates duplication when implementing interfaces or overriding virtual members.

Interface implementation:

public interface IWidgetService
{
    /// <summary>
    /// Creates a new widget with the specified name.
    /// </summary>
    /// <param name="name">The display name for the widget.</param>
    /// <returns>The created widget.</returns>
    Task<Widget> CreateWidgetAsync(string name);
}

public class WidgetService : IWidgetService
{
    /// <inheritdoc />
    public async Task<Widget> CreateWidgetAsync(string name)
    {
        // Implementation inherits all documentation from the interface
    }
}

Base class override:

public abstract class RepositoryBase<T>
{
    /// <summary>
    /// Retrieves an entity by its unique identifier.
    /// </summary>
    /// <param name="id">The entity identifier.</param>
    /// <returns>The entity if found; otherwise, <see langword="null"/>.</returns>
    public abstract Task<T?> GetByIdAsync(Guid id);
}

public class OrderRepository : RepositoryBase<Order>
{
    /// <inheritdoc />
    public override async Task<Order?> GetByIdAsync(Guid id)
    {
        // Inherits summary, param, and returns docs from base class
    }
}

Selective inheritance with cref:

/// <inheritdoc cref="IWidgetService.CreateWidgetAsync(string)"/>
/// <remarks>
/// This implementation validates the name and assigns a default category
/// before persisting to the database.
/// </remarks>
public async Task<Widget> CreateWidgetAsync(string name)
{
}

Inheritance with path filter:

/// <inheritdoc cref="IWidgetService.CreateWidgetAsync(string)" path="/summary"/>
/// <param name="name">Custom param doc that overrides the interface.</param>
public async Task<Widget> CreateWidgetAsync(string name)
{
}

<see> and <seealso>

Create inline references and "See Also" links.

/// <summary>
/// Validates the widget against the rules defined in <see cref="WidgetValidator"/>.
/// Use <see cref="WidgetService.CreateWidgetAsync(string)"/> to create validated widgets.
/// </summary>
/// <seealso cref="WidgetValidator"/>
/// <seealso cref="IValidationResult"/>
/// <seealso href="https://docs.mylib.dev/validation">Validation Guide</seealso>
public ValidationResult Validate(Widget widget)
{
}

<see> variants:

/// <summary>
/// Returns <see langword="true"/> if the widget is active,
/// <see langword="false"/> otherwise.
/// Use <see cref="Activate"/> to change the state.
/// The value is stored as a <see cref="bool"/>.
/// </summary>
public bool IsActive { get; }

<c> and <code>

Format inline code and code blocks within documentation.

/// <summary>
/// Parses a widget name from the format <c>"category:name"</c>.
/// </summary>
/// <remarks>
/// The expected input format:
/// <code>
/// "analytics:page-views"    // category = "analytics", name = "page-views"
/// "default:my-widget"       // category = "default", name = "my-widget"
/// "my-widget"               // category = null, name = "my-widget" (no colon)
/// </code>
/// </remarks>
public (string? Category, string Name) ParseWidgetName(string input)
{
}

<paramref> and <typeparamref>

Reference parameters and type parameters within documentation text.

/// <summary>
/// Converts <paramref name="entity"/> to a DTO of type <typeparamref name="TDto"/>.
/// If <paramref name="entity"/> is <see langword="null"/>, returns the default value
/// of <typeparamref name="TDto"/>.
/// </summary>
/// <typeparam name="TDto">The target DTO type.</typeparam>
/// <param name="entity">The source entity to convert.</param>
public TDto? ToDto<TDto>(object? entity)
{
}

<list>

Create bulleted, numbered, or table lists within documentation.

/// <summary>
/// Applies the specified transformation to the widget.
/// </summary>
/// <remarks>
/// Supported transformations:
/// <list type="bullet">
/// <item><description>Resize -- changes the widget dimensions</description></item>
/// <item><description>Recolor -- applies a new color scheme</description></item>
/// <item><description>Reposition -- moves the widget to new coordinates</description></item>
/// </list>
/// </remarks>
public void ApplyTransformation(Widget widget, Transformation transform)
{
}

Comprehensive XML Doc Example

A complete class demonstrating all tag types working together:

using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

namespace MyLibrary;

/// <summary>
/// Manages the lifecycle of widgets including creation, retrieval, update, and deletion.
/// All operations are thread-safe and support cancellation via <see cref="CancellationToken"/>.
/// </summary>
/// <remarks>
/// <para>
/// <see cref="WidgetService"/> requires a registered <see cref="IWidgetRepository"/>
/// and <see cref="ILogger{TCategoryName}"/> via dependency injection.
/// </para>
/// <para>
/// Widget names must be unique within a category. Attempting to create a widget with a
/// duplicate name in the same category throws <see cref="InvalidOperationException"/>.
/// </para>
/// </remarks>
/// <example>
/// Register and use the service:
/// <code>
/// // Registration
/// builder.Services.AddScoped&lt;IWidgetService, WidgetService&gt;();
///
/// // Usage
/// var widget = await widgetService.CreateWidgetAsync(
///     "My Widget",
///     category: "Dashboard");
/// </code>
/// </example>
/// <seealso cref="IWidgetRepository"/>
/// <seealso cref="Widget"/>
public class WidgetService : IWidgetService
{
    private readonly IWidgetRepository _repository;
    private readonly ILogger<WidgetService> _logger;

    /// <summary>
    /// Initializes a new instance of <see cref="WidgetService"/>.
    /// </summary>
    /// <param name="repository">The widget data repository.</param>
    /// <param name="logger">The logger for diagnostic output.</param>
    /// <exception cref="ArgumentNullException">
    /// Thrown when <paramref name="repository"/> or <paramref name="logger"/> is
    /// <see langword="null"/>.
    /// </exception>
    public WidgetService(IWidgetRepository repository, ILogger<WidgetService> logger)
    {
        _repository = repository ?? throw new ArgumentNullException(nameof(repository));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    /// <summary>
    /// Gets the total number of widgets in the system.
    /// </summary>
    /// <value>A non-negative integer representing the total widget count.</value>
    public int TotalCount => _repository.Count;

    /// <inheritdoc />
    public async Task<Widget> CreateWidgetAsync(
        string name,
        string? category = null,
        CancellationToken cancellationToken = default)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(name);

        _logger.LogInformation("Creating widget {Name} in category {Category}", name, category);

        var widget = new Widget
        {
            Id = Guid.NewGuid(),
            Name = name,
            Category = category ?? "default",
            CreatedAt = DateTimeOffset.UtcNow,
            Status = WidgetStatus.Draft
        };

        await _repository.AddAsync(widget, cancellationToken);
        return widget;
    }

    /// <summary>
    /// Retrieves all widgets matching the specified filter criteria.
    /// </summary>
    /// <param name="filter">
    /// The filter to apply. Use <see cref="WidgetFilter.None"/> for unfiltered results.
    /// </param>
    /// <param name="cancellationToken">A token to cancel the operation.</param>
    /// <returns>
    /// A read-only list of widgets matching the filter. Returns an empty list if no
    /// widgets match the criteria.
    /// </returns>
    /// <exception cref="ArgumentNullException">
    /// Thrown when <paramref name="filter"/> is <see langword="null"/>.
    /// </exception>
    public async Task<IReadOnlyList<Widget>> ListAsync(
        WidgetFilter filter,
        CancellationToken cancellationToken = default)
    {
        ArgumentNullException.ThrowIfNull(filter);
        return await _repository.FindAsync(filter, cancellationToken);
    }
}

XML Doc Conventions for Public Libraries

Documentation Requirements

For NuGet packages consumed by other developers, follow these conventions:

1. Every public type must have a <summary> -- this is the minimum for IntelliSense to display useful information
2. Every public method parameter must have a <param> -- describe what the parameter controls, valid ranges, and null behavior
3. Every method that can throw must document exceptions with <exception> -- callers need to know what to catch
4. Return values must have <returns> -- describe the return value semantics, especially for nullable returns
5. Properties should have <value> -- describe what the property represents and its default value
6. Generic type parameters must have <typeparam> -- describe constraints and expected usage
7. Complex APIs should include <example> -- show real usage, not trivial one-liners
8. Use <remarks> for caveats and threading behavior -- important context that does not belong in the summary

Writing Style

• Use third person declarative: "Gets the widget name" not "Get the widget name" or "This gets the widget name"
• Start <summary> with a verb: "Creates...", "Retrieves...", "Validates...", "Computes..."
• Avoid restating the obvious: do not write "Gets the Name property" for a property called Name
• Document behavior, not implementation: "Returns the cached value if available" not "Checks the dictionary and returns the value"
• Use <see cref="..."/> for all type and member references -- enables IDE navigation and refactoring support
• Use <see langword="null"/>, <see langword="true"/>, <see langword="false"/> instead of bare null, true, false

CancellationToken Convention

Standardize documentation for CancellationToken parameters:

/// <param name="cancellationToken">A token to cancel the asynchronous operation.</param>

This one-line description is sufficient for the standard CancellationToken cancellationToken = default pattern. Do not over-document what cancellation means -- callers understand the pattern.

Auto-Generation Tooling

IDE Quick-Fix Generation

All major .NET IDEs generate XML doc skeletons when you type /// above a member:

Visual Studio / VS Code (C# Dev Kit):

• Type /// above a method, class, or property
• The IDE generates a <summary> skeleton with <param>, <returns>, <typeparam> tags pre-filled based on the member's signature

JetBrains Rider:

• Type /// to trigger the same skeleton generation
• Rider additionally warns about missing XML docs and offers quick-fixes to add them

GhostDoc-Style Patterns

GhostDoc and similar tools generate documentation text from member names using naming convention heuristics:

• GetWidgetById generates "Gets the widget by identifier"
• IsActive generates "Gets a value indicating whether this instance is active"
• CreateWidgetAsync generates "Creates the widget asynchronously"

These auto-generated descriptions are a starting point. Always review and improve generated text to add domain-specific context, parameter constraints, exception conditions, and examples.

EditorConfig Integration

Enforce XML documentation requirements through .editorconfig:

# .editorconfig
[*.cs]
# Require XML documentation for public members
dotnet_diagnostic.CS1591.severity = warning

# For public libraries, treat as error:
# dotnet_diagnostic.CS1591.severity = error

IntelliSense Integration

How XML Docs Surface in IDEs

XML documentation comments are the primary source of IntelliSense tooltips:

• Hover tooltips: Display <summary> text when hovering over a type or member
• Parameter hints: Display <param> text in the parameter info popup during method calls
• Completion list: Display <summary> in the autocomplete dropdown
• Quick Info: Display <returns>, <exception>, and <remarks> in expanded documentation panels
• Signature help: Display parameter names and types with <param> descriptions

NuGet Package IntelliSense

When <GenerateDocumentationFile> is enabled and the package is published to NuGet, the XML file is included in the package. Consumers get full IntelliSense support without needing source access:

<!-- The XML doc file is automatically included in the NuGet package -->
<PropertyGroup>
  <GenerateDocumentationFile>true</GenerateDocumentationFile>
  <!-- The XML file appears in the package's lib/net8.0/ directory -->
</PropertyGroup>

No additional NuGet packaging configuration is needed -- dotnet pack includes the XML doc file automatically when GenerateDocumentationFile is true.

Source Link Integration

Combine XML docs with Source Link for the best developer experience:

<PropertyGroup>
  <GenerateDocumentationFile>true</GenerateDocumentationFile>
  <!-- Source Link enables "Go to Definition" into package source -->
  <PublishRepositoryUrl>true</PublishRepositoryUrl>
  <EmbedUntrackedSources>true</EmbedUntrackedSources>
  <IncludeSymbols>true</IncludeSymbols>
  <SymbolPackageFormat>snupkg</SymbolPackageFormat>
</PropertyGroup>

With both XML docs and Source Link enabled, consumers can hover for documentation and navigate to the original source code.

Agent Gotchas

1. Always enable <GenerateDocumentationFile> for public libraries -- without it, NuGet consumers get no IntelliSense documentation. Add it to Directory.Build.props to apply across all projects in a solution.

2. Use <inheritdoc /> for interface implementations and overrides -- do not duplicate documentation text between an interface and its implementation. Duplication causes maintenance drift.

3. Do not suppress CS1591 globally for public NuGet packages -- global suppression via <NoWarn>CS1591</NoWarn> hides all missing documentation warnings. Use per-file #pragma suppression for intentionally undocumented types, or make internal types truly internal.

4. Use <see cref="..."/> for all type references, not bare type names -- <see cref="Widget"/> enables IDE navigation and is validated at build time. Bare text "Widget" is not linked and can become stale if the type is renamed.

5. Use <see langword="null"/> instead of bare null in documentation text -- this renders with proper formatting in IntelliSense and API doc sites. Same applies to true, false, and other C# keywords.

6. <inheritdoc> resolves at build time, not design time -- some older IDE versions may show "Documentation not found" for <inheritdoc> in tooltips. The documentation is correctly resolved in the generated XML file and in API doc sites.

7. XML doc comments must use < and > for generic type syntax in prose -- but <see cref="..."/> handles generics automatically. Use <see cref="List{T}"/> (curly braces), not <see cref="List&lt;T&gt;"/>.

8. In <code> blocks, use < and > for angle brackets -- XML doc comments are XML, so < and > in code examples must be escaped. Alternatively, use <![CDATA[...]]> to avoid escaping.

9. Do not generate API documentation sites from XML comments -- API doc site generation (DocFX, OpenAPI-as-docs) belongs to [skill:dotnet-api-docs]. This skill covers the XML comment authoring side only.

10. Document cancellation tokens with a single standard line -- use "A token to cancel the asynchronous operation." for all CancellationToken parameters. Do not over-document the cancellation pattern.