C#•10mo ago•

72 replies

``Type.IsAssignableFrom`` returning false unexpectedly in plugin-loading scenario

This is a plugin framework. The "base" DLL with a plugin class that is subclassed by plugin DLLs is located in

{ROOT}/bin/fhcore.dll

{ROOT}/bin/fhcore.dll

, while plugins are located in

{ROOT}/modules/{PLUGIN_NAME}/{PLUGIN_NAME.dll}

{ROOT}/modules/{PLUGIN_NAME}/{PLUGIN_NAME.dll}

.

This plugin framework is loaded into the application process by .NET hosting, if that is somehow meaningful.

All plugins have project references with

<Private>false</Private>

<Private>false</Private>

and

<ExcludeAssets>runtime</ExcludeAssets>

<ExcludeAssets>runtime</ExcludeAssets>

, ex.

        <ProjectReference Include="..\core\Fahrenheit.Core.csproj">
            <Private>false</Private>
            <ExcludeAssets>runtime</ExcludeAssets>
        </ProjectReference>

        <ProjectReference Include="..\core\Fahrenheit.Core.csproj">
            <Private>false</Private>
            <ExcludeAssets>runtime</ExcludeAssets>
        </ProjectReference>

I first ensure

bin/fhcore.dll

bin/fhcore.dll

is loaded into

AssemblyLoadContext.Default

AssemblyLoadContext.Default

.

Then for each plugin, I instantiate an

AssemblyLoadContext

AssemblyLoadContext

as such:

public class FhLoadContext(string dll_path) : AssemblyLoadContext {
    private readonly AssemblyDependencyResolver _resolver = new AssemblyDependencyResolver(dll_path);

    protected override Assembly? Load(AssemblyName assembly_name) {
        string? assembly_path = _resolver.ResolveAssemblyToPath(assembly_name);
        return assembly_path != null ? LoadFromAssemblyPath(assembly_path) : null;
    }

    protected override nint LoadUnmanagedDll(string dll_name) {
        string? dll_path = _resolver.ResolveUnmanagedDllToPath(dll_name);
        return dll_path != null ? LoadUnmanagedDllFromPath(dll_path) : nint.Zero;
    }
}

public class FhLoadContext(string dll_path) : AssemblyLoadContext {
    private readonly AssemblyDependencyResolver _resolver = new AssemblyDependencyResolver(dll_path);

    protected override Assembly? Load(AssemblyName assembly_name) {
        string? assembly_path = _resolver.ResolveAssemblyToPath(assembly_name);
        return assembly_path != null ? LoadFromAssemblyPath(assembly_path) : null;
    }

    protected override nint LoadUnmanagedDll(string dll_name) {
        string? dll_path = _resolver.ResolveUnmanagedDllToPath(dll_name);
        return dll_path != null ? LoadUnmanagedDllFromPath(dll_path) : nint.Zero;
    }
}

I then

LoadFromAssemblyPath

LoadFromAssemblyPath

the plugin into the context, and afterwards:
- I clearly see that only the plugin itself (and any non-plugin-core dependencies thereof) are in the

FhLoadContext

FhLoadContext

- A duplicate reference to the core did not sneak in.

Yet,

typeof(BaseModule).IsAssignableFrom(plugin_type)

typeof(BaseModule).IsAssignableFrom(plugin_type)

still returns

false

false

for a given

public class PluginModule : BaseModule

public class PluginModule : BaseModule

in the plugin DLL. Why could that be?

``Type.IsAssignableFrom`` returning false unexpectedly in plugin-loading scenario

This is a plugin framework. The "base" DLL with a plugin class that is subclassed by plugin DLLs is located in

{ROOT}/bin/fhcore.dll

{ROOT}/bin/fhcore.dll

, while plugins are located in

{ROOT}/modules/{PLUGIN_NAME}/{PLUGIN_NAME.dll}

{ROOT}/modules/{PLUGIN_NAME}/{PLUGIN_NAME.dll}

.

This plugin framework is loaded into the application process by .NET hosting, if that is somehow meaningful.

All plugins have project references with

<Private>false</Private>

<Private>false</Private>

and

<ExcludeAssets>runtime</ExcludeAssets>

<ExcludeAssets>runtime</ExcludeAssets>

, ex.

        <ProjectReference Include="..\core\Fahrenheit.Core.csproj">
            <Private>false</Private>
            <ExcludeAssets>runtime</ExcludeAssets>
        </ProjectReference>

        <ProjectReference Include="..\core\Fahrenheit.Core.csproj">
            <Private>false</Private>
            <ExcludeAssets>runtime</ExcludeAssets>
        </ProjectReference>

I first ensure

bin/fhcore.dll

bin/fhcore.dll

is loaded into

AssemblyLoadContext.Default

AssemblyLoadContext.Default

.

Then for each plugin, I instantiate an

AssemblyLoadContext

AssemblyLoadContext

as such:

public class FhLoadContext(string dll_path) : AssemblyLoadContext {
    private readonly AssemblyDependencyResolver _resolver = new AssemblyDependencyResolver(dll_path);

    protected override Assembly? Load(AssemblyName assembly_name) {
        string? assembly_path = _resolver.ResolveAssemblyToPath(assembly_name);
        return assembly_path != null ? LoadFromAssemblyPath(assembly_path) : null;
    }

    protected override nint LoadUnmanagedDll(string dll_name) {
        string? dll_path = _resolver.ResolveUnmanagedDllToPath(dll_name);
        return dll_path != null ? LoadUnmanagedDllFromPath(dll_path) : nint.Zero;
    }
}

public class FhLoadContext(string dll_path) : AssemblyLoadContext {
    private readonly AssemblyDependencyResolver _resolver = new AssemblyDependencyResolver(dll_path);

    protected override Assembly? Load(AssemblyName assembly_name) {
        string? assembly_path = _resolver.ResolveAssemblyToPath(assembly_name);
        return assembly_path != null ? LoadFromAssemblyPath(assembly_path) : null;
    }

    protected override nint LoadUnmanagedDll(string dll_name) {
        string? dll_path = _resolver.ResolveUnmanagedDllToPath(dll_name);
        return dll_path != null ? LoadUnmanagedDllFromPath(dll_path) : nint.Zero;
    }
}

I then

LoadFromAssemblyPath

LoadFromAssemblyPath

the plugin into the context, and afterwards:
- I clearly see that only the plugin itself (and any non-plugin-core dependencies thereof) are in the

FhLoadContext

FhLoadContext

- A duplicate reference to the core did not sneak in.

Yet,

typeof(BaseModule).IsAssignableFrom(plugin_type)

typeof(BaseModule).IsAssignableFrom(plugin_type)

still returns

false

false

for a given

public class PluginModule : BaseModule

public class PluginModule : BaseModule

in the plugin DLL. Why could that be?

``Type.IsAssignableFrom`` returning false unexpectedly in plugin-loading scenario

``Type.IsAssignableFrom`` returning false unexpectedly in plugin-loading scenario

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