revit-dependency-isolation

# Revit Dependency Isolation Add-ins share one process; two add-ins using different versions of the same dependency crash Revit. Revit 2027+ isolates each add-in in its own `AssemblyLoadContext`; earlier versions need dependencies repacked into the add-in assembly. The `Nice3point.Revit.Sdk` provides both. ## When to use - A dependency version conflict with another add-in crashes Revit. - Choosing between isolation (2027+) and repacking (legacy) for a distributable add-in. ## When not to use - A single dependency fails to load (a `FileNotFoundException`) — use `revit-assembly-resolution`. ## Workflow ### Step 1: Isolate on Revit 2027+ Revit 2027+ isolation is declared in the `.addin` manifest. Add a `ManifestSettings` block that gives the add-in its own load context: ```xml <ManifestSettings> <UseRevitContext>False</UseRevitContext> <ContextName>RevitAddin</ContextName> </ManifestSettings> ``` `UseRevitContext=False` loads the add-in in its own `AssemblyLoadContext` named by `ContextName`; it can then use any dependency version without colliding with other add-ins. Adding `ManifestSettings` on Revit versions older than 2027 crashes Revit — the SDK strips the node during publish for older years (see `revit-addin-publishing`). This is separate from `<EnableDynamicLoading>true</EnableDynamicLoading>` — a stock .NET SDK property every modern add-in sets; it emits the add-in's dependencies to the output folder. That property is a prerequisite for loading dependencies at all, not the isolation mechanism (see `revit-sdk-project-configuration`). ### Step 2: Repack for legacy Revit (pre-2027) Revit 2026 and earlier provide no load-context isolation. Merge the dependencies into the add-in assembly with ILRepack. ```xml <IsRepackable Condition="'$(RevitVersion)' &lt; '2027'">true</IsRepackable> <RepackBinariesExcludes>$(AssemblyName).UI.dll;System*.dll</RepackBinariesExcludes> ``` Repacking requires the `ILRepack` package. Prefer isolation on 2027+ over repacking. ### Step 3: Verify Load the add-in alongside another that uses a different version of the same dependency, and confirm both load without conflict. ## Validation - [ ] Revit 2027+ add-ins isolate with the `.addin` `ManifestSettings` block (not `EnableDynamicLoading`, which is a separate prerequisite). - [ ] Legacy add-ins use `IsRepackable` with an appropriate excludes list. - [ ] `ManifestSettings` is not shipped raw to Revit versions older than 2027 (the SDK patches it on publish). ## Common Pitfalls | Pitfall | Correct approach | |---------------------------------------------------------|------------------------------------------------------------------------------------------------------| | `ManifestSettings` shipped to Revit < 2027 | Let the SDK patch the manifest on publish; keep the block for 2027+. | | Treating `EnableDynamicLoading` as the isolation switch | It only emits dependencies to the output folder; isolate with the manifest `ManifestSettings` block. | | Repacking a .NET Core add-in | Use isolation on 2027+, not ILRepack. | | Repacking the UI or `System.*` assemblies | Exclude them via `RepackBinariesExcludes`. |