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Embedded files with Roslyn compilation

I am looking for an example in how to compile a project using Roslyn. The code below is an example I found in https://github.com/dotnet/roslyn/wiki/FAQ … This examples doesn't cover embedded files. Is that possible?
public class MyTask : Task {
public override bool Execute() {
var projectFileName = this.BuildEngine.ProjectFileOfTaskNode;
var project = ProjectCollection.GlobalProjectCollection.
GetLoadedProjects(projectFileName).Single();
var compilation = CSharpCompilation.Create(
project.GetPropertyValue("AssemblyName"),
syntaxTrees: project.GetItems("Compile").Select(
c => SyntaxFactory.ParseCompilationUnit(
c.EvaluatedInclude).SyntaxTree),
references: project.GetItems("Reference")
.Select(
r => new MetadataFileReference
(r.EvaluatedInclude)));
// Now work with compilation ...
}
}

Yes, it is possible to embed resources into result assembly using Roslyn.
To produce a result assembly CSharpCompilation type has an Emit method. This method has many parameters. One of them is manifestResources, which is responsible for adding embedded resources. You mas specify as many resources as you want. The following code demonstrates how you can use this parameter to emit an assembly with an embedded resource into peStream. It creates a resource with name "resourceName" and content that located at "path-to-resource" path.
void ProduceAssembly(CSharpCompilation compilation, Stream peStream)
{
ResourceDescription[] resources =
{
new ResourceDescription(
"resourceName",
() => File.OpenRead("path-to-resource"),
isPublic: true
)
};
var result = compilation.Emit(peStream, manifestResources: resources);
if (!result.Success)
{
var diagnostics = string.Join(Environment.NewLine, result.Diagnostics);
throw new Exception($"Compilation failed with: {diagnostics}");
}
}
Don't forget to check EmitResult.Success property to ensure that compilation completed successfully. Also ensure that peStream is disposed properly after compilation.

Adding Assemblies/Types to be made available to Razor Page at Runtime

I'm trying to build a dynamic Web interface where I can dynamically point at a folder and serve Web content out of that folder with ASP.NET Core. This works fairly easily by using FileProviders in ASP.NET Core to re-route the Web root folder. This works both for StaticFiles and For RazorPages.
However, for RazorPages the problem is that once you do this you can't dynamically add references for additional types. I'd like to be able to optionally add a folder (PrivateBin) which on startup I can loop through, load the assemblies and then have those assemblies visible in Razor.
Unfortunately it doesn't work as Razor does not appear to see the loaded assemblies even when using runtime compilation.
I use the following during startup to load assemblies. Note the folder that these are loaded from are not in the default ContentRoot or WebRoot but in the new redirected WebRoot.
// WebRoot is a user chosen Path here specified via command line --WebRoot c:\temp\web
private void LoadPrivateBinAssemblies()
{
var binPath = Path.Combine(WebRoot, "PrivateBin");
if (Directory.Exists(binPath))
{
var files = Directory.GetFiles(binPath);
foreach (var file in files)
{
if (!file.EndsWith(".dll", StringComparison.CurrentCultureIgnoreCase) &&
!file.EndsWith(".exe", StringComparison.InvariantCultureIgnoreCase))
continue;
try
{
var asm = AssemblyLoadContext.Default.LoadFromAssemblyPath(file);
Console.WriteLine("Additional Assembly: " + file);
}
catch (Exception ex)
{
Console.WriteLine("Failed to load private assembly: " + file);
}
}
}
}
The assembly loads into the AssemblyLoadContext() and I can - using Reflection and Type.GetType("namespace.class,assembly") - access the type.
However, when I try to access the type in RazorPages - even with Runtime Compilation enabled - the types are not available. I get the following error:
To make sure that the type is indeed available, I checked that I can do the following inside of Razor:
#{
var md = Type.GetType("Westwind.AspNetCore.Markdown.Markdown,Westwind.AspNetCore.Markdown");
var mdText = md.InvokeMember("Parse", BindingFlags.InvokeMethod | BindingFlags.Public | BindingFlags.Static, null,
null, new object[] { "**asdasd**", false, false, false });
}
#mdText
and that works fine. So the assembly is loaded and the type is accessible, but Razor doesn't appear to be aware of it.
So the question is:
Is it possible to load assemblies at runtime and make them available to Razor with Runtime Compilation, and use it like you normally would use a type via direct declarative access?

It turns out the solution to this is via the Razor Runtime Compilation Options which allow adding of extra 'ReferencePaths', and then explicitly loading assemblies.
In ConfigureServices():
services.AddRazorPages(opt => { opt.RootDirectory = "/"; })
.AddRazorRuntimeCompilation(
opt =>
{
opt.FileProviders.Add(new PhysicalFileProvider(WebRoot));
LoadPrivateBinAssemblies(opt);
});
then:
private void LoadPrivateBinAssemblies(MvcRazorRuntimeCompilationOptions opt)
{
var binPath = Path.Combine(WebRoot, "PrivateBin");
if (Directory.Exists(binPath))
{
var files = Directory.GetFiles(binPath);
foreach (var file in files)
{
if (!file.EndsWith(".dll", StringComparison.CurrentCultureIgnoreCase) &&
!file.EndsWith(".exe", StringComparison.InvariantCultureIgnoreCase))
continue;
try
{
var asm = AssemblyLoadContext.Default.LoadFromAssemblyPath(file);
opt.AdditionalReferencePaths.Add(file);
}
catch (Exception ex)
{
...
}
}
}
}
The key is:
opt.AdditionalReferencePaths.Add(file);
which makes the assembly visible to Razor, but doesn't actually load it. To load it you then have to explicitly load it with:
AssemblyLoadContext.Default.LoadFromAssemblyPath(file);
which loads the assembly from a path. Note that any dependencies that this assembly has have to be available either in the application's startup path or in the same folder you're loading from.
Note: Load order for dependencies may be important here or a not previously added assembly may not be found as a dependency (untested).

A Quick look into the ASP.NET Core source code reveals:
All Razor view Compilations start at:
RuntimeViewCompiler.CreateCompilation(..)
which uses:
CSharpCompiler.Create(.., .., references: ..)
which uses:
RazorReferenceManager.CompilationReferences
which uses: see code on github
// simplyfied
var referencePaths = ApplicationPartManager.ApplicationParts
.OfType<ICompilationReferencesProvider>()
.SelectMany(_ => _.GetReferencePaths())
which uses:
ApplicationPartManager.ApplicationParts
So we need somehow register our own ICompilationReferencesProvider and this is how..
ApplicationPartManager
While it's search for Application parts does the ApplicationPartManager a few things:
it searchs for hidden Assemblies reading attributes like:
[assembly: ApplicationPartAttribute(assemblyName:"..")] // Specifies an assembly to be added as an ApplicationPart
[assembly: RelatedAssemblyAttribute(assemblyFileName:"..")] // Specifies a assembly to load as part of MVC's assembly discovery mechanism.
// plus `Assembly.GetEntryAssembly()` gets added automaticly behind the scenes.
Then it loops throuth all found Assemblies and uses ApplicationPartFactory.GetApplicationPartFactory(assembly) (as seen in line 69) to find types which extend ApplicationPartFactory.
Then it invokes the method GetApplicationParts(assembly) on all found ApplicationPartFactorys.
All Assemblies without ApplicationPartFactory get the DefaultApplicationPartFactory which returns new AssemblyPart(assembly) in GetApplicationParts.
public abstract IEnumerable<ApplicationPart> GetApplicationParts(Assembly assembly);
GetApplicationPartFactory
GetApplicationPartFactory searches for [assembly: ProvideApplicationPartFactory(typeof(SomeType))] then it uses SomeType as factory.
public abstract class ApplicationPartFactory {
public abstract IEnumerable<ApplicationPart> GetApplicationParts(Assembly assembly);
public static ApplicationPartFactory GetApplicationPartFactory(Assembly assembly)
{
// ...
var provideAttribute = assembly.GetCustomAttribute<ProvideApplicationPartFactoryAttribute>();
if (provideAttribute == null)
{
return DefaultApplicationPartFactory.Instance; // this registers `assembly` as `new AssemblyPart(assembly)`
}
var type = provideAttribute.GetFactoryType();
// ...
return (ApplicationPartFactory)Activator.CreateInstance(type);
}
}
One Solution
This means we can create and register (using ProvideApplicationPartFactoryAttribute) our own ApplicationPartFactory which returns a custom ApplicationPart implementation which implements ICompilationReferencesProvider and then returns our references in GetReferencePaths.
[assembly: ProvideApplicationPartFactory(typeof(MyApplicationPartFactory))]
namespace WebApplication1 {
public class MyApplicationPartFactory : ApplicationPartFactory {
public override IEnumerable<ApplicationPart> GetApplicationParts(Assembly assembly)
{
yield return new CompilationReferencesProviderAssemblyPart(assembly);
}
}
public class CompilationReferencesProviderAssemblyPart : AssemblyPart, ICompilationReferencesProvider {
private readonly Assembly _assembly;
public CompilationReferencesProviderAssemblyPart(Assembly assembly) : base(assembly)
{
_assembly = assembly;
}
public IEnumerable<string> GetReferencePaths()
{
// your `LoadPrivateBinAssemblies()` method needs to be called before the next line executes!
// So you should load all private bin's before the first RazorPage gets requested.
return AssemblyLoadContext.GetLoadContext(_assembly).Assemblies
.Where(_ => !_.IsDynamic)
.Select(_ => new Uri(_.CodeBase).LocalPath);
}
}
}
My Working Test Setup:
ASP.NET Core 3 WebApplication
ASP.NET Core 3 ClassLibrary
Both Projects have no reference to each other.
<Project Sdk="Microsoft.NET.Sdk.Web">
<PropertyGroup>
<TargetFramework>netcoreapp3.0</TargetFramework>
</PropertyGroup>
<ItemGroup>
<Content Remove="Pages\**" />
</ItemGroup>
<ItemGroup>
<PackageReference Include="Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation" Version="3.0.0" />
</ItemGroup>
</Project>
services
.AddRazorPages()
.AddRazorRuntimeCompilation();
AssemblyLoadContext.Default.LoadFromAssemblyPath(#"C:\path\to\ClassLibrary1.dll");
// plus the MyApplicationPartFactory and attribute from above.
~/Pages/Index.cshtml
#page
<pre>
output: [
#(
new ClassLibrary1.Class1().Method1()
)
]
</pre>
And it shows the expected output:
output: [
Hallo, World!
]
Have a nice day.

AssemblyLoadContext Dispose .dll

In a MVC controller I use AssemblyLoadContext.Default.LoadFromAssemblyPath(pathToDll); to load an assembly. I want to delete or replace the given .dll file during runtime. This is not possible because the file is not disposed. Is there any way to dispose the .dll file? There are solutions using the AppDomain class, which is not available in asp.net core.
Background:
The user is able to upload a custom .dll file which contains implementations of a given interface. The user should also be able to replace his file. I use the following code in a controller to access the implementations:
var conventions = new ConventionBuilder();
conventions
.ForTypesDerivedFrom<IPluginContract>()
.Export<IPluginContract>()
.Shared();
var configuration = new ContainerConfiguration().WithAssembliesInPath(path, conventions);
using (var container = configuration.CreateContainer())
{
var plugins = container.GetExports<IPluginContract>();
return plugins;
}
With
public static ContainerConfiguration WithAssembliesInPath(
this ContainerConfiguration configuration,
string path, AttributedModelProvider conventions,
SearchOption searchOption = SearchOption.TopDirectoryOnly)
{
var fileNames = Directory
.GetFiles(path, "*.dll", searchOption);
List<Assembly> assemblies = new List<Assembly>();
foreach (string relativePath in fileNames)
{
Assembly assembly = AssemblyLoadContext.Default.LoadFromAssemblyPath(Path.GetFullPath(relativePath));
assemblies.Add(assembly);
}
configuration = configuration.WithAssemblies(assemblies, conventions);
return configuration;
}

OPTION 1:
Try loading dll with method LoadFromStream, then you can remove dll without exceptions.
Ex:
foreach (string relativePath in fileNames)
{
using (var fs = File.Open(relativePath , FileMode.Open))
{
Assembly assembly = AssemblyLoadContext.Default.LoadFromStream(fs);
assemblies.Add(assembly);
}
File.Delete(relativePath); //It doesn't throw exception
}
NOTE: tested with Net Core 3.1 but could work with previous versions.
OPTION 2:
If you have a problem when try to reload assemblies with LoadFromStream you should try to call AssemblyLoadContext.Default.Unload() before to LoadFromStream()
But I'm not sure if it works with AssemblyLoadContext.Default, so if you still keep any exception you should create any class that inherit from AssemblyLoadContext with flag isCollectible to true like this:
public class PluginLoadContext : AssemblyLoadContext
{
public PluginLoadContext() : base(isCollectible: true)
{
}
}
And the code should be:
//var pluginContext = new PluginLoadContext(); //In some place to call unload later
pluginContext.Unload();
foreach (string relativePath in fileNames)
{
using (var fs = File.Open(relativePath , FileMode.Open))
{
Assembly assembly = pluginContext.LoadFromStream(fs);
assemblies.Add(assembly);
}
File.Delete(relativePath); //It doesn't throw exception
}
OPTION 3:
There is another option that override Load method of your custom PluginLoadContext, you only need to load your entry dll, and the reference dll is knew with deps.json file of your entry dll.
In this example is using MemoryStream to prevent attach plugin dll.
public class PluginLoadContext : AssemblyLoadContext
{
private AssemblyDependencyResolver _resolver;
public PluginLoadContext(string pluginPath) : base(isCollectible: true)//isCollectible doesn't appear in netstandard2.1
{
_resolver = new AssemblyDependencyResolver(pluginPath);
}
protected override Assembly Load(AssemblyName assemblyName)
{
string assemblyPath = _resolver.ResolveAssemblyToPath(assemblyName);
if (assemblyPath != null)
{
//Using MemoryStream to prevent attach dll to this .exe
MemoryStream ms = new MemoryStream();
using (var fs = File.Open(assemblyPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
{
fs.CopyTo(ms);
}
ms.Position = 0;
return LoadFromStream(ms);
}
return null;
}
}
Then you can load your entry plugin dll like this.
var dllPath = "<path to your entry dll>" // dll and deps.json file together .
var pc = new PluginLoadContext(dllPath);
var assembly = pc.LoadFromAssemblyName(new AssemblyName(Path.GetFileNameWithoutExtension(dllPath)));
//You can load a reference dll too if you need it
var referenceAssembly = pc.LoadFromAssemblyName(new AssemblyName(Path.GetFileNameWithoutExtension("<path of reference dll>")));
REF:
https://learn.microsoft.com/en-us/dotnet/core/tutorials/creating-app-with-plugin-support#load-plugins

When you load a dll into your application domain, this dll is not free before the appDomain is being destroyed (i.e. your process is stopped) there is no dispose for a dll.
For references on how to reach your desired functionality please have a look at these questions that are answered already:
Using AppDomain to dynamically load and unload dll
Hot unload and reload of a dll used by an application

It sounds very similar to MEF ( Managed Extensibility Framework ). It allows inject DLL's and also helps to manage the lifecycle.
Example:
public static class MefInjection
{
private static CompositionContainer mycontainer;
public static CompositionContainer MyContainer
{
get
{
if (mycontainer == null)
{
var catalog =
new DirectoryCatalog(".", "MyMEFProject.*");
mycontainer = new CompositionContainer(catalog);
}
return mycontainer;
}
}
}
The preceding code will grab all the exported values from all the assemblies in the same directory starting with "MyMEFProject". Then you can use mycontainer to get loaded DLL's functionality.

Compile Assembly on the fly

I have this code:
static void Main(string[] args)
{
CompilerParameters cp = new CompilerParameters
{
GenerateInMemory = true,
IncludeDebugInformation = false,
};
cp.ReferencedAssemblies.AddRange(new string[]{
"System.dll",
"System.Data.dll",
"System.Xml.dll",
"Microsoft.mshtml.dll",
"System.Windows.Forms.dll"
});
Assembly _assembly = Assembly.GetExecutingAssembly();
StreamReader _textStreamReader = new StreamReader(_assembly.GetManifestResourceStream("myprog.restext.txt"));
string src = _textStreamReader.ReadToEnd();
byte[] code = Convert.FromBase64String(src);
src = Encoding.UTF8.GetString(code);
CompilerResults cr = CSharpCodeProvider.CreateProvider("CSharp").
CompileAssemblyFromSource(cp, src);
Assembly asm = cr.CompiledAssembly;
Type typ = asm.GetType("clicker.Program");
MethodInfo method = typ.GetMethod("DoStart");
method.Invoke(null, new[] { (object)args });
}
I thows FileNotFoundException becouse CompileAssemblyFromSource returns the same error. Source using mshtml.
Then I'm trying to compile it using csc.exe, it says:
error CS0006. (no Metadata for "Microsoft.mshtml.dll")
I think it because mshtml is ActiveX library. So The question is how to assemble source usings activeX mshtml.
p.s.
Source has no errors and successfully has compiled from VS but can't be compiled by "on the fly" compilation.

I thows FileNotFoundException
That's normal, Microsoft.mshtml.dll is a primary interop assembly. It is not part of the .NET Framework so cannot be located automatically. It also won't be available on the user's machine, PIAs have to be installed.
The best way to go about it is to ensure that the assembly is present in your build directory so it will be deployed along with your program and can always be found. Project + Add Reference, select Microsoft.mshtml. Select it from the References node and set the Isolated property to False, Copy Local to True. Rebuild and verify that you now have Microsoft.mshtml.dll present in your bin\Debug directory.
And modify your code to pass the full path name to the file. Like this:
var referenceAssemblies = new List<string> {
"System.dll",
"System.Data.dll",
"System.Xml.dll",
"System.Windows.Forms.dll"
};
var homedir = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
var mshtml = Path.Combine(homedir, "Microsoft.mshtml.dll");
referenceAssemblies.Add(mshtml);
cp.ReferencedAssemblies.AddRange(referenceAssemblies.ToArray());

How to dynamically load references in parent assemblies in C#

How do I get a list of references in the parent assembly in C#. I'm thinking of a DLL that is loaded into another program, and the driver needs to use some of the parent assembly references in reflection and serialization. So far, I haven't tried anything as I'm not sure where to start.

It's pretty classic reflection issue, when you need to load an assembly and the assembly contains references, which are not referenced to the calling assembly.
Basically, you should load the assembly inside separate application domain.
e.g., you have a project ProxyDomain with a class ProxyType:
public class ProxyType : MarshalByRefObject
{
public void DoSomeStuff(string assemblyPath)
{
var someStuffAssembly = Assembly.LoadFrom(assemblyPath);
//Do whatever you need with the loaded assembly, e.g.:
var someStuffType = assembly.GetExportedTypes()
.First(t => t.Name == "SomeStuffType");
var someStuffObject = Activator.CreateInstance(someStuffType);
someStuffType.GetMethod("SomeStuffMethod").Invoke(someStuffObject, null);
}
}
And in your calling project, which contains a reference to ProxyDomain, you need to load the assembly, execute DoSomeStuff and unload the assembly resources:
public class SomeStuffCaller
{
public void CallDoSomeStuff(string assemblyPath)
{
AppDomainSetup setup = AppDomain.CurrentDomain.SetupInformation;
//Path to the directory, containing the assembly
setup.ApplicationBase = "...";
//List of directories where your private references are located
setup.PrivateBinPath = "...";
setup.ShadowCopyFiles = "true";
var reflectionDomain = AppDomain.CreateDomain("ProxyDomain", null, setup);
//You should specify the ProxyDomain assembly full name
//You can also utilize CreateInstanceFromAndUnwrap here:
var proxyType = (ProxyType)reflectionDomain.CreateInstanceAndUnwrap(
"ProxyDomain",
"ProxyType");
proxyType.DoSomeStuff(assemblyPath);
AppDomain.Unload(reflectionDomain);
}
}