dotnet-inspect

name	dotnet-inspect
description	Query .NET APIs across NuGet packages, platform libraries, and local files. Search for types, list API surfaces, compare and diff versions, find extension methods and implementors. Use whenever you need to answer questions about .NET library contents.

dotnet-inspect

Query .NET library APIs — the same commands work across NuGet packages, platform libraries (System., Microsoft.AspNetCore.), and local .dll/.nupkg files.

Quick Decision Tree

• Code broken? → diff --package Foo@old..new first, then member
• What's new in a .NET preview? → diff --platform System.Runtime@P2..P3 --additive per framework library
• What types exist? → type --package Foo (discover types in a package or library)
• What members does a type have? → member Type --package Foo (compact table by default)
• What does a type look like? → type Type --package Foo (tree view for single type)
• What are the method signatures? → member Type --package Foo -m Method (full signatures + docs)
• What is the source/IL? → member Type --package Foo -m Method:1 -v:d (Source, Lowered C#, IL)
• Where is the source code? → source Type --package Foo (SourceLink URLs), source Type -m Member (with line numbers)
• Want raw source content? → source Type --package Foo --cat (fetches and prints source files)
• What constructors exist? → member 'Type<T>' --package Foo -m .ctor (use <T> not <>)
• How many overloads? → member Type --package Foo --show-index (shows Name:N indices)
• What does this package depend on? → depends --package Foo
• What does this type inherit? → depends 'INumber<TSelf>'
• Want a dependency diagram? → depends --mermaid (standalone) or depends --markdown --mermaid (embedded)
• What metadata fields exist? → -S Section --fields "PDB*" (structured query, no DSL)
• What version is available? → Foo --version (cache-first), Foo --latest-version (always NuGet), Foo --versions (list all)

When to Use This Skill

• "What types are in this package?" — type discovers types, find searches by pattern
• "What members does this type have?" — member for methods/properties/events (docs on by default)
• "What changed between versions?" — diff classifies breaking/additive changes
• "What new APIs shipped in this preview?" — diff --platform System.Runtime@prev..current --additive per framework library
• "This code uses an old API — fix it" — diff the old..new version, then member to see the new API
• "What extends this type?" — extensions finds extension methods/properties (--reachable for transitive)
• "What implements this interface?" — implements finds concrete types
• "What does this type depend on?" — depends walks type hierarchy, package deps, or library refs
• "Show dependencies as a diagram" — depends --mermaid for standalone mermaid, --markdown --mermaid for embedded
• "Where is the source code?" — source returns SourceLink URLs; add member name for line numbers
• "What version/metadata does this have?" — package and library inspect metadata
• "What version is available?" — Foo --version (fast, cache-first — like docker run)
• "What's the latest on NuGet?" — Foo --latest-version (always queries NuGet — like docker pull)
• "What versions exist?" — Foo --versions (list all published versions)
• "What TFMs are available?" — package Foo --tfms, then type --package Foo --tfm net8.0
• "Where is the source code?" — source returns SourceLink URLs; add member name for line numbers
• "Show me the actual source?" — source Type --package Foo --cat fetches and prints source file contents
• "Show me something cool" — demo runs curated showcase queries

Key Patterns

Default output is markdown — headings, tables, and field lists that render well in terminals, editors, and LLM contexts. No flags needed:

dnx dotnet-inspect -y -- member JsonSerializer --package System.Text.Json    # scan members
dnx dotnet-inspect -y -- type --package System.Text.Json                     # scan types
dnx dotnet-inspect -y -- diff --package System.CommandLine@2.0.0-beta4.22272.1..2.0.3  # triage changes

Default format is markdown — no flags needed. Optional formats: oneline (--oneline), plaintext (--plaintext), json (--json), mermaid (--mermaid). Verbosity (-v:q/m/n/d) controls which sections are included; formatter controls how they render. They compose freely — except --oneline and -v cannot be combined.

dnx dotnet-inspect -y -- member JsonSerializer --package System.Text.Json -v:d  # detailed (source/IL)
dnx dotnet-inspect -y -- System.Text.Json -v:n --plaintext                      # all local sections, plaintext
dnx dotnet-inspect -y -- type --package System.Text.Json --oneline              # compact columnar output
dnx dotnet-inspect -y -- depends Stream --mermaid                               # standalone mermaid diagram
dnx dotnet-inspect -y -- depends Stream --markdown --mermaid                    # mermaid embedded in markdown

Use diff first when fixing broken code — triage changes, then drill into specifics:

dnx dotnet-inspect -y -- diff --package System.CommandLine@2.0.0-beta4.22272.1..2.0.3  # what changed?
dnx dotnet-inspect -y -- member Command --package System.CommandLine@2.0.3               # new API surface

Platform Diffs & Release Notes

For framework libraries (System., Microsoft.AspNetCore.), use --platform instead of --package. This is the primary workflow for .NET release notes — diff each framework library between preview versions:

dnx dotnet-inspect -y -- diff --platform System.Runtime@P2..P3 --additive        # what's new?
dnx dotnet-inspect -y -- diff --platform System.Net.Http@P2..P3 --additive       # per-library
dnx dotnet-inspect -y -- diff --platform System.Text.Json@9.0.0..10.0.0          # across major versions

Multi-library packages: diff --package works across all libraries in a package (e.g., Microsoft.Azure.SignalR with multiple DLLs). For framework ref packages like Microsoft.NETCore.App.Ref, prefer --platform per-library since it resolves from installed packs.

Nightly/preview packages from custom feeds: The --source flag works for version listing but not package downloads. Pre-populate the NuGet cache instead:

# Pre-populate cache (fails with NU1213 but downloads the package)
dotnet add package Microsoft.NETCore.App.Ref --version <version> --source <feed-url>
# Then use normally — resolves from NuGet cache
dnx dotnet-inspect -y -- diff --platform System.Runtime@P2..P3 --additive

Version Resolution (Docker-style)

Version queries use Docker-like semantics: cached packages are served in under 15ms, network calls cost 1–4 seconds. Three flags, three behaviors:

Flag	Behavior	Network	Like Docker...
--version (bare)	Local — returns the version from local cache	Only on cache miss	docker run nginx
--latest-version	Remote — queries nuget.org for the absolute latest	Always	docker pull nginx
--versions	Remote — returns every published version	Always	docker image ls --all

--version and bare-name inspection share the same cache. If Foo --version returns 2.0.3, then Foo (or package Foo) will inspect that same 2.0.3 — no surprises, no extra network call. This is the fast path for most tasks.

--latest-version and --versions always query nuget.org, so they reflect the latest published state. Use --latest-version when you need to confirm the newest version, e.g., before a dependency upgrade.

dnx dotnet-inspect -y -- Foo --version           # what's in the cache? (fast, local)
dnx dotnet-inspect -y -- Foo --latest-version     # what's on nuget.org? (always network)
dnx dotnet-inspect -y -- Foo --versions           # list all published versions
dnx dotnet-inspect -y -- Foo --versions 5         # list latest 5 versions
dnx dotnet-inspect -y -- Foo --versions --preview # include prerelease versions

The same flags work on the package subcommand:

dnx dotnet-inspect -y -- package Foo --version           # same local cache check
dnx dotnet-inspect -y -- package Foo --latest-version     # always queries nuget.org
dnx dotnet-inspect -y -- package Foo --versions           # list all versions

Version pinning with @version syntax:

dnx dotnet-inspect -y -- Foo@2.0.3                # pinned — no network if cached
dnx dotnet-inspect -y -- Foo@latest               # always checks nuget.org
dnx dotnet-inspect -y -- Foo                      # prefer cache, refresh on TTL expiry

Use --version (not --latest-version) as the default. It's fast and returns the same version that bare-name commands will use. Only reach for --latest-version when you need the absolute latest from nuget.org.

Structured Queries (like Go templates, without a DSL)

Discover the schema, then select and project — no template language needed:

dnx dotnet-inspect -y -- System.Text.Json -D                          # list sections
dnx dotnet-inspect -y -- System.Text.Json -D --effective              # sections with data (dry run)
dnx dotnet-inspect -y -- library System.Text.Json -D --tree           # full schema tree
dnx dotnet-inspect -y -- System.Text.Json -S Symbols                  # render one section
dnx dotnet-inspect -y -- System.Text.Json -S Symbols --fields "PDB*"  # project specific fields
dnx dotnet-inspect -y -- type System.Text.Json --columns Kind,Type    # project specific columns

Mermaid Diagrams

The depends command supports --mermaid for Mermaid diagram output. Two modes:

Flags	Output	Use case
--mermaid	Standalone mermaid (graph TD)	Pipe to mmdc, embed in tooling
--markdown --mermaid	Mermaid fenced blocks inside markdown	Render in GitHub, VS Code, docs

dnx dotnet-inspect -y -- depends Stream --mermaid                               # type hierarchy as mermaid
dnx dotnet-inspect -y -- depends Stream --markdown --mermaid                    # embedded in markdown
dnx dotnet-inspect -y -- depends --library System.Text.Json --mermaid           # assembly reference graph
dnx dotnet-inspect -y -- depends --package Markout --mermaid                    # package dependency graph

Search Scope

Search commands (find, extensions, implements, depends) use scope flags:

• (no flags) — all platform frameworks (runtime, aspnetcore, netstandard)
• --platform — all platform frameworks
• --extensions — curated Microsoft.Extensions.* packages
• --aspnetcore — curated Microsoft.AspNetCore.* packages
• --package Foo — specific NuGet package (combinable with scope flags)

type, member, library, diff accept --platform <name> as a string for a specific platform library.

Command Reference

Command	Purpose
type	Discover types — terse output, no docs, use --shape for hierarchy
member	Inspect members — docs on by default, supports dotted syntax (-m Type.Member)
find	Search for types by glob or fuzzy match across any scope
diff	Compare API surfaces between versions — breaking/additive classification
extensions	Find extension methods/properties for a type (--reachable for transitive)
implements	Find types implementing an interface or extending a base class
depends	Walk dependency graphs upward — type hierarchy, package deps, or library refs
package	Package metadata, files, versions, dependencies, search for NuGet discovery
library	Library metadata, symbols, references, SourceLink audit
source	SourceLink URLs — type-level or member-level (with line numbers), --cat to fetch content, --verify to check URLs
demo	Run curated showcase queries — list, invoke, or feeling-lucky

Filtering and Limiting

dnx dotnet-inspect -y -- type System.Text.Json -k enum               # filter by kind (type and member commands)
dnx dotnet-inspect -y -- type System.Text.Json -t "*Converter*"      # glob filter on type names
dnx dotnet-inspect -y -- member System.Text.Json JsonDocument -m Parse  # filter by member name
dnx dotnet-inspect -y -- type System.Text.Json -5                    # first 5 lines (like head -5)
dnx dotnet-inspect -y -- type System.Text.Json --tail 10             # last 10 lines (like tail -10)

Do not pipe output through head, tail, or Select-Object. Use built-in --head / --tail:

• -n N, --head N, or -N — first N lines (like head). Keeps headers, truncates cleanly.
• --tail N — last N lines (like tail). Buffers output, emits only the final N lines.
• -m N (numeric) — item limit (members per kind section).
• -k Kind — filter by kind: class/struct/interface/enum/delegate (type) or method/property/field/event/constructor (type single-type view, member).
• -S Section — show only a specific section (glob-capable).

Key Syntax

• Generic types need quotes: 'Option<T>', 'IEnumerable<T>'
• Use <T> not <> for generic types — "Option<>" resolves to the abstract base, 'Option<T>' resolves to the concrete generic with constructors
• type uses -t for type filtering, member uses -m for member filtering (not --filter)
• Dotted syntax for member: -m JsonSerializer.Deserialize or -m System.Text.Json.JsonSerializer.Deserialize
• Diff ranges use ..: --package System.Text.Json@9.0.0..10.0.0
• Derived types only show their own members — query the base type too

Installation

Use dnx (like npx). Always use -y and -- to prevent interactive prompts:

dnx dotnet-inspect -y -- <command>

Related Skills

• dotnet-reviewer — Uses dotnet-inspect to investigate API surface and version diffs during reviews
• dotnet-sdk-builder — Queries types and members of existing libraries when generating SDK wrappers
• dotnet-nuget-manager — Inspects packages before upgrading or replacing them
• dotnet-aspnet — Discovers ASP.NET Core APIs across versions when migrating or adopting new features