revit-dependency-isolation

name	revit-dependency-isolation
description	Prevent Autodesk Revit add-in dependency conflicts with AssemblyLoadContext isolation (Revit 2027+) or ILRepack repacking (legacy). USE FOR: resolving crashes caused by two add-ins loading different versions of the same dependency, by isolating your add-in's assemblies. DO NOT USE FOR: resolving a missing dependency at load time (use revit-assembly-resolution).
license	MIT

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 simply 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:

<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 add-ins and lower without isolation, merge dependencies into the add-in with ILRepack.

<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.