dotnet-inspect: Compare .NET APIs and Implementations Across Versions

Use this skill to establish what changed, then judge the consequences. Run dnx dotnet-inspect -y -- <command>. Skills provide productive starts; installed explanation supplies detailed analyses, bindings and limits.

Compare the public API

dnx dotnet-inspect -y -- diff \
  --package System.Text.Json@9.0.0..10.0.0 --breaking
dnx dotnet-inspect -y -- diff \
  --platform System.Runtime@9.0.0..10.0.0 --additive
dnx dotnet-inspect -y -- diff --library old/Foo.dll..new/Foo.dll -S Changes

--breaking selects assessed breaks; --additive selects additions. Use -S Changes for the complete API change population, including unclassified changes. Unclassified does not mean safe or breaking. Narrow with -t Type; use --all for non-public, hidden and obsolete declarations.

Single-Library API comparisons require compatible assembly identities. Incomplete or rejected comparisons are not compared, not "no changes." Read completion, diagnostics and exit status. Unprojected --json gives the typed comparison outcome; where supported, --envelope adds Share and diagnostics. Sectioned/filtered JSON can use a presentation schema instead.

Follow one API across versions

dnx dotnet-inspect -y -- member System.Text.Json.JsonSerializer Deserialize:1 \
  --package System.Text.Json@9.0.0..10.0.0 --match

Subject-owned --match follows API correspondence from the source coordinate. Resolve the selector only at the source: the same overload ordinal on the destination is not identity. This matches declarations, not accessor bodies. Root match instead compares implementation bodies or discovers similar members; similar code is not API correspondence or semantic equivalence.

Look beyond API shape

dnx dotnet-inspect -y -- diff --package Foo@1.0.0..2.0.0 \
  -S "Analysis Diff"
dnx dotnet-inspect -y -- diff --library old/Foo.dll..new/Foo.dll \
  --implementation -t MyType -m HotPath
dnx dotnet-inspect -y -- explain "compare string literals"

Analysis Diff surfaces allocation, unsafe, exception and other static shifts. Implementation Diff compares reconstructed C#, IL and explicitly requested PDB Source. Changed literals can identify endpoint changes, not actual network traffic. Read the returned analysis and CLI binding for required predicates before executing an unfamiliar analysis; do not guess the filter grammar.

Decompiled C# is not authored source. PDB Source is checksum-matched to the Portable PDB; source absence is not deletion. Neither identical IL nor similar source proves behavioral equivalence. Load skill decompiler or skill sourcelink when fidelity or provenance is material.

Choose versions and locate a boundary

Use package Foo --versions -n 1 for one newest listed version row, package Foo@latest --versions for a fresh check, or an exact Foo@version pin for reproducibility. --preview opts into prereleases. Load skill private-feeds when source authority matters.

dnx dotnet-inspect -y -- package Foo@1.0.0..2.0.0 --versions
dnx dotnet-inspect -y -- diff --history --package Foo@1.0.0..2.0.0 \
  --type Foo.Parser --members --major-versions
dnx dotnet-inspect -y -- diff --history --package Foo@1.0.0..2.0.0 \
  -t Foo.Parser -m Parse --finding analysis.allocation --at first --at last

History can follow API presence, members, attributes and body Findings. --at selects an exact version, one-based #N, first or last. Checkpoint transitions establish changes between probes, not the exact introduction version. Omitting checkpoints may evaluate the full population; choose an explicit bound before expensive history work.

For recurrence-safe onset, walk backward from the bad version to a successful absence. Binary search needs a known monotonic predicate. Preserve the same source, visibility and framework across probes; listed-only vectors can differ from an --include-unlisted listing.

Confirm a candidate adjacent boundary with the native Finding comparison:

dnx dotnet-inspect -y -- diff --package Foo@1.4.0..1.5.0 \
  -t Foo.Parser -m Parse --finding analysis.allocation

PairFinding.Added with Old=absent and New=present establishes an added occurrence. Present, Removed and Changed remain different outcomes; aggregate count deltas do not establish onset. Use installed analysis discovery for other Finding families and their required target grain.

Report assessed breaks, other API changes, implementation observations and unresolved runtime questions separately. A sparse history or failed comparison must not become an all-versions compatibility claim.