Unmanaged (native) library loading algorithm

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Unmanaged libraries are located and loaded with an algorithm involving various stages.

The following algorithm describes how native libraries are loaded through PInvoke.

PInvoke load library algorithm

PInvoke uses the following algorithm when attempting to load an unmanaged assembly:

• Determine the active AssemblyLoadContext. For an unmanaged load library, the active AssemblyLoadContext is the caller of the PInvoke.

• For the active AssemblyLoadContext, try to find the assembly in priority order by:

  • Checking its cache.

  • Calling the current System.Runtime.InteropServices.DllImportResolver delegate set by the NativeLibrary.SetDllImportResolver(Assembly, DllImportResolver) function.

  • Calling the AssemblyLoadContext.LoadUnmanagedDll function.

  • Checking the AppDomain instance's cache and running the Unmanaged (native) library probing logic.

  • Raising the AssemblyLoadContext.ResolvingUnmanagedDll event for the active AssemblyLoadContext.

• If the unmanaged library is newly loaded, the AppDomain.AssemblyLoad event is raised.