revit-assembly-resolution

# Revit Assembly Resolution Revit does not probe an add-in's folder for dependencies; loading a window or third-party assembly can throw `FileNotFoundException`. `ResolveHelper` (from `Nice3point.Revit.Toolkit`) redirects resolution to a type-adjacent or explicit folder for the scope's lifetime. Scopes nest — the innermost is searched first. ## When to use - A dependency or WPF window fails to load with a resolution error. - Isolating a conflicting assembly version for a bounded operation. ## When not to use - Inside an entry point derived from the Toolkit base classes (`ExternalCommand`, `AsyncExternalCommand`, `ExternalApplication`, `ExternalDBApplication`) — they already open a resolve scope; a manual one is redundant. - Preventing two add-ins from loading conflicting versions of the same dependency process-wide — that is `revit-dependency-isolation`. ## Workflow ### Step 1: Wrap the load in a resolve scope ```csharp using (ResolveHelper.BeginAssemblyResolveScope<Application>()) { var window = new SettingsWindow(); window.Show(); } ``` The generic and `typeof(...)` overloads probe the folder of the given type's assembly. Pass an explicit directory when the dependencies live elsewhere — a shared or external libraries folder: ```csharp using (ResolveHelper.BeginAssemblyResolveScope(@"C:\Libraries")) { return LoadExternalLibrary(); } ``` ### Step 2: Scope it tightly and nest for isolation Open the scope only around the load that needs it, and nest scopes when a dependency version must be isolated from an outer one. ### Step 3: Verify Confirm the dependency loads without a resolution error, and that resolution behavior is restored after the scope disposes. ## Validation - [ ] The scope wraps the specific load that fails to resolve. - [ ] Entry points rely on the base classes, not a manual scope. - [ ] The scope disposes, restoring normal resolution. ## Common Pitfalls | Pitfall | Correct approach | |------------------------------------------------------------------|-----------------------------------------------------------| | A hand-written `AppDomain.CurrentDomain.AssemblyResolve` handler | Use `ResolveHelper.BeginAssemblyResolveScope`. | | Adding a scope inside a Toolkit entry point | The base class already resolves; remove it. | | `ResolveHelper` not found | The `Nice3point.Revit.Toolkit` package is not referenced. |