| name | msbuild-loader-netframework |
| description | How MSBuildLocator loads MSBuild assemblies and discovers installs on .NET Framework (the net46 target / #if NET46 / non-NETCOREAPP branches in src/MSBuildLocator). Covers the AppDomain.AssemblyResolve handler, search-path probing, and Developer Console + Visual Studio Setup (COM) discovery. Use when editing or reviewing net46 loader, registration, or VS-discovery code, or diagnosing assembly-resolution behavior on .NET Framework hosts. |
.NET Framework (net46) MSBuild loader
Scope: src/MSBuildLocator/MSBuildLocator.cs #if NET46 and Framework (#else
of NETCOREAPP) branches. FEATURE_VISUALSTUDIOSETUP is defined only when
TargetFramework == net46 in Microsoft.Build.Locator.csproj. For build/test
and cross-cutting conventions, see AGENTS.md.
Assembly-resolution handler
s_registeredHandler is a static ResolveEventHandler; IsRegistered is
s_registeredHandler != null.RegisterMSBuildPathsInternally stores the handler in the static field before
subscribing to AppDomain.CurrentDomain.AssemblyResolve; the event subscription
keeps the delegate alive, while the field tracks registration state.AssemblyResolve can fire repeatedly for the same assembly; results are cached
in loadedAssemblies keyed by AssemblyName.FullName.- Resolution is explicitly not thread-safe; every cache lookup/load runs under
lock (loadedAssemblies).
- Handler path: parse
eventArgs.Name with new AssemblyName(eventArgs.Name);
for each registered search path, if <msbuildPath>\<Name>.dll exists, return
Assembly.LoadFrom(targetAssembly).
- Search paths come from
RegisterMSBuildPath(...), or from
RegisterInstance(...) as instance.MSBuildPath plus the VS NuGet path when
it exists.
Discovery sources (net46 only)
- Developer command prompt:
GetDevConsoleInstance() reads VSINSTALLDIR, then
parses VSCMD_VER (trimming any suffix after -), then falls back to
VisualStudioVersion; yields DiscoveryType.DeveloperConsole.
- Visual Studio Setup COM API: under
FEATURE_VISUALSTUDIOSETUP,
VisualStudioLocationHelper.GetInstances() enumerates VS 2017+ setup instances
with Microsoft.Component.MSBuild; yields DiscoveryType.VisualStudioSetup.
DiscoveryType.DotNetSdk exists in the enum but belongs to the Core path; net46
GetInstances(...) does not call SDK discovery.
What net46 does NOT do
- No
AssemblyLoadContext, hostfxr, or .NET SDK discovery — those are
#if NETCOREAPP paths (see the msbuild-loader-netcore skill).
Register-before-load contract
CanRegister is false once any strong-named Microsoft.Build* assembly in
s_msBuildAssemblies is loaded in the current AppDomain.- JIT caveat: a method that references
Microsoft.Build types can trip the
contract when JIT-compiled, even if that reference never executes. Keep locator
calls isolated before any such reference.
