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ResolveEventHandler not invoked when object is created in new AppDomain

I hope it wouldn't be a duplicate, I see plenty of similar questions, but any of them help can't help me.
I have such Method code in nameofdll.dll:
DllMethod()
{
Assembly assembly = Assembly.GetExecutingAssembly();
Type type = assembly.GetType("Class");
MethodInfo method = type.GetMethod("Method");
object obj = Activator.CreateInstance(type);
method.Invoke(...);
}
and Class - constructor add AssemblyResolver
class Class
{
public Class()
{
AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(MyResolveEventHandler);
}
public void Method()
{...}
private Assembly MyResolveEventHandler(object sender, ResolveEventArgs args)
{...}
}
Till now AssemblyResolver is invoked when I call metod from my main app.exe which is in the same folder as nameofdll.dll, let's name the folder as mainfolder and also from powershell script in this way:
load dll(mainfolder + nameofdll.dll)
call DllMethod()
Everything works fine, but I have to unload dll which AssemblyResolver had loaded, because Method is called multiple times witch different dlls versions.
So I modified DllMethod() like that:
{
Assembly assembly = Assembly.GetExecutingAssembly();
MethodInfo method = type.GetMethod("Method");
//new part
AppDomainSetup domainSetup = new AppDomainSetup();
domainSetup.ApplicationBase = Path.GetDirectoryName(assembly.Location);
AppDomain Domain = AppDomain.CreateDomain(Class, null, domainSetup);
object obj = Domain.CreateInstanceAndUnwrap(assembly.FullName, Class);
method.Invoke(...);
AppDomain.Unload(Domain);
}
I use
domainSetup.ApplicationBase = Path.GetDirectoryName(assembly.Location);
because BaseDirecotry was powershell folder and CreateInstanceAndUnwrap fails to find nameofdll.dll.
And finally the problem is that everyting is ok when using app.exe, but when I called that dll method from powershell script, the AssemblyResolver wasn't invoked and immediately I got error that it could not load some dlls.
I also try to copy domain setting, and add
AppDomainSetup domainSetup = AppDomain.CurrentDomain.SetupInformation;
where CurrentDomain is domain in which AssemblyResolver works fine before, but it didn't solve the problem.

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.

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);
}
}

compiling/merging dll into standalone exe with wpf

Background : Merging dlls into a single .exe with wpf
How shall i merge a .dll reference into the .exe file, i read the above post, got principle behind it, but i am not able to figure out how to do it?( i am newbie, sorry)
The reference file is HtmlagilityPack.dll
Currently my App.xaml.cs contains :
public partial class App : Application
{
public App(){
AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(ResolveAssembly);
// proceed starting app...
}
static Assembly ResolveAssembly(object sender, ResolveEventArgs args)
{
//We dont' care about System Assembies and so on...
if (!args.Name.ToLower().StartsWith("Html")) return null;
Assembly thisAssembly = Assembly.GetExecutingAssembly();
//Get the Name of the AssemblyFile
var name = args.Name.Substring(0, args.Name.IndexOf(',')) + ".dll";
//Load form Embedded Resources - This Function is not called if the Assembly is in the Application Folder
var resources = thisAssembly.GetManifestResourceNames().Where(s => s.EndsWith(name));
if (resources.Count() > 0)
{
var resourceName = resources.First();
using (Stream stream = thisAssembly.GetManifestResourceStream(resourceName))
{
if (stream == null) return null;
var block = new byte[stream.Length];
stream.Read(block, 0, block.Length);
return Assembly.Load(block);
}
}
return null;
}
}
Where else am i supposed to make changes?, i have being trying past an hour with an example of http://blog.mahop.net/post/Merge-WPF-Assemblies.aspx But not able to figure out how to do it with HtmlAgilityPack.

Okay, finally had to use the SmartAssembly program.
But still looking for a solution to do it by code.

Your code looks slightly off, it should look more like this:
public class App : Application
{
[STAThreadAttribute()]
public static void Main()
{
AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(ResolveAssembly);
// etc...
}
// etc...
You then also need to change the "Startup object" setting in the properties page of your project to use the App class (i.e. the above code) - you should then see the Main method of this class being the first code executed when you start debugging.

AppDomain.CurrentDomain.AssemblyResolve asking for a <AppName>.resources assembly?

using the code How to embed a satellite assembly into the EXE file provided by csharptest.net, I've created a custom assembly resolver and embedded my assemblies in my resources.
I can successfully resolve my assemblies used in but somehow AppDomain.CurrentDomain.AssemblyResolve asks for an assembly called 'AppName.resources' specifically "MyProgram.resources, Version=0.15.3992.31638, Culture=en-US, PublicKeyToken=null" which i don't know how to resolve?
I've tried to disable loading my custom assemblies from resources (placed all my assembly dll's in program directory) and just enabled AppDomain.CurrentDomain.AssemblyResolve, but it was still asking for it.
I'm a bit confused about this, will appreciate a lot if you can help me on this.
Here's my code for interested ones;
static Assembly ResolveAssemblies(object sender, ResolveEventArgs args)
{
Assembly assembly = null;
string name = args.Name.Substring(0, args.Name.IndexOf(','));
if (name == "MyProgram.resources") return null;
else name = string.Format("MyProgram.Resources.Assemblies.{0}.dll", name);
lock (_loadedAssemblies)
{
if (!_loadedAssemblies.TryGetValue(name, out assembly))
{
using (Stream io = Assembly.GetExecutingAssembly().GetManifestResourceStream(name))
{
if (io == null)
{
MessageBox.Show("MyProgram can not load one of it's dependencies. Please re-install the program", string.Format("Missing Assembly: {0}", name), MessageBoxButtons.OK, MessageBoxIcon.Error);
Environment.Exit(-1);
}
using (BinaryReader binaryReader = new BinaryReader(io))
{
assembly = Assembly.Load(binaryReader.ReadBytes((int)io.Length));
_loadedAssemblies.Add(name, assembly);
}
}
}
}
return assembly;
}

Answering on my own;
Adding this line to AssemblyInfo.cs solves it and resolver will not get asked for resources any-more.
[assembly: NeutralResourcesLanguageAttribute("en-US", UltimateResourceFallbackLocation.MainAssembly)]
Though this is a work-around should be carefully considered multi-language applications.
More Info:
https://connect.microsoft.com/VisualStudio/feedback/details/526836/wpf-appdomain-assemblyresolve-being-called-when-it-shouldnt
http://blogs.msdn.com/b/kimhamil/archive/2008/11/11/what-does-the-neutralresourceslanguageattribute-do.aspx
http://forums.devshed.com/net-development-87/c-wpf-appdomain-assemblyresolve-being-called-when-it-shouldn-t-669567.html
http://blogs.msdn.com/b/microsoft_press/archive/2010/02/03/jeffrey-richter-excerpt-2-from-clr-via-c-third-edition.aspx
This approach fails for machines with non en-US cultures. A better approach is ignoring resources on assembly resolver;
public Assembly Resolver(object sender, ResolveEventArgs args)
{
lock (this)
{
Assembly assembly;
AssemblyName askedAssembly = new AssemblyName(args.Name);
string[] fields = args.Name.Split(',');
string name = fields[0];
string culture = fields[2];
// failing to ignore queries for satellite resource assemblies or using [assembly: NeutralResourcesLanguage("en-US", UltimateResourceFallbackLocation.MainAssembly)]
// in AssemblyInfo.cs will crash the program on non en-US based system cultures.
if (name.EndsWith(".resources") && !culture.EndsWith("neutral")) return null;
/* the actual assembly resolver */
...
}
}

My situation was a bit more complex and the above solution did not work for me. (That is changing the AssemblyInfo.cs file)
I have moved all my form and image resources to a seperate dll and the moment any of the images are used the 'filenotfoundexception' exception is thrown.
The important information is the following:
Beginning with the .NET Framework 4, the ResolveEventHandler event is raised for all assemblies, including resource assemblies. See the following reference
https://msdn.microsoft.com/en-us/library/system.appdomain.assemblyresolve(v=vs.110).aspx
The solution turned out to be very simple. If a resource file is requested in the form 'dllname.resources.dll' always return null;
Here is the event code that I have adapted from other samples found. (I have commented the debugging lines - un-comment them if you have a problem using the code.
Add this line in your class. It is used to prevent loading a dll more than once
readonly static Dictionary<string, Assembly> _libs = new Dictionary<string, Assembly>();
This is the event method.
private static Assembly OnAssemblyResolve(object sender, ResolveEventArgs args)
{
Assembly assembly = null;
string keyName = new AssemblyName(args.Name).Name;
if (keyName.Contains(".resources"))
{
return null; // This line is what fixed the problem
}
if (_libs.ContainsKey(keyName))
{
assembly = _libs[keyName]; // If DLL is loaded then don't load it again just return
return assembly;
}
string dllName = DllResourceName(keyName);
//string[] names = Assembly.GetExecutingAssembly().GetManifestResourceNames(); // Uncomment this line to debug the possible values for dllName
using (Stream stream = Assembly.GetExecutingAssembly().GetManifestResourceStream(dllName))
{
if (stream == null)
{
Debug.Print("Error! Unable to find '" + dllName + "'");
// Uncomment the next lines to show message the moment an assembly is not found. (This will also stop for .Net assemblies
//MessageBox.Show("Error! Unable to find '" + dllName + "'! Application will terminate.");
//Environment.Exit(0);
return null;
}
byte[] buffer = new BinaryReader(stream).ReadBytes((int) stream.Length);
assembly = Assembly.Load(buffer);
_libs[keyName] = assembly;
return assembly;
}
}
private static string DllResourceName(string ddlName)
{
if (ddlName.Contains(".dll") == false) ddlName += ".dll";
foreach (string name in Assembly.GetExecutingAssembly().GetManifestResourceNames())
{
if (name.EndsWith(ddlName)) return name;
}
return ddlName;
}