C# Roslyn Compile - Use Nuget Package within dynamically compiled Code - compiles but throws an Exception at runtime (Could not load file or assembly)

Question

I try to accomplish using a Nuget Package in dynamic compiled code using Roslyn Compiler.

I want to use a Nuget Package ( in my example https://www.nuget.org/packages/TinyCsvParser/ ) within my code. So I downloaded the package and extracted it to a folder (C:\Data\packages\tinycsvparser.2.6.1)

But I don't want it to be in my applications direct dependencies. So it is not referenced in the project itself and I don't want to copy it to the bin/Debug-Folder.

The Nuget-Package-DLL should be able to be anywhere on my harddisk.

The compilation runs without any errors. But on Runtime on the line method.Invoke(fooInstance, null) I get the following Exception:

Could not load file or assembly 'TinyCsvParser, Version=2.6.1.0, Culture=neutral, PublicKeyToken=d7df35b038077099' or one of its dependencies. The system cannot find the file specified.

How can I tell the programm where it should look for the DLL? I tried it with the following line

Assembly nugetAssembly = Assembly.LoadFrom(pathToNugetDLL);

But that did not help.

Thank you for any advice on how to resolve this issue.

Here is my Code (Prototype):

using System;
using System.Collections.Generic;
using System.IO;
using System.Reflection;
using System.Text;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.Emit;
using Microsoft.CodeAnalysis.Text;

namespace Playground
{
   public static class Program
   {
      private const string pathToNugetDLL = @"C:\Data\packages\tinycsvparser.2.6.1\lib\net45\TinyCsvParser.dll";

      private const string firstClass =
@"
using TinyCsvParser;

namespace A
{
    public class MyClass
    {
        public int MyFunction()
         {
            CsvParserOptions csvParserOptions = new CsvParserOptions(true, ';');
            return 1;
         }
    }
}";

      public static void Main()
      {
         CSharpParseOptions parseOptions = new CSharpParseOptions(LanguageVersion.CSharp7, DocumentationMode.Parse, SourceCodeKind.Regular);
         SyntaxTree parsedSyntaxTree = SyntaxFactory.ParseSyntaxTree(firstClass, parseOptions);

         List<string> defaultNamespaces = new List<string>() { };

         //// Referenzen über Kommentare heraussuchen:
         List<MetadataReference> defaultReferences = CreateMetadataReferences();

         var encoding = Encoding.UTF8;

         var assemblyName = Path.GetRandomFileName();
         var symbolsName = Path.ChangeExtension(assemblyName, "pdb");
         var sourceCodePath = "generated.cs";

         var buffer = encoding.GetBytes(firstClass);
         var sourceText = SourceText.From(buffer, buffer.Length, encoding, canBeEmbedded: true);

         var syntaxTree = CSharpSyntaxTree.ParseText(
             sourceText,
             new CSharpParseOptions(),
             path: sourceCodePath);

         var syntaxRootNode = syntaxTree.GetRoot() as CSharpSyntaxNode;
         var encoded = CSharpSyntaxTree.Create(syntaxRootNode, null, sourceCodePath, encoding);


         CSharpCompilationOptions defaultCompilationOptions =
               new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
                       .WithOverflowChecks(true).WithOptimizationLevel(OptimizationLevel.Debug).WithPlatform(Platform.AnyCpu)
                       .WithUsings(defaultNamespaces);

         CSharpCompilation compilation = CSharpCompilation.Create(
             assemblyName,
             syntaxTrees: new[] { encoded },
             references: defaultReferences,

             options: defaultCompilationOptions
         );

         using (var assemblyStream = new MemoryStream())
         using (var symbolsStream = new MemoryStream())
         {
            var emitOptions = new EmitOptions(
                    debugInformationFormat: DebugInformationFormat.Pdb,
                    pdbFilePath: symbolsName);

            var embeddedTexts = new List<EmbeddedText> { EmbeddedText.FromSource(sourceCodePath, sourceText) };

            EmitResult result = compilation.Emit(
                peStream: assemblyStream,
                pdbStream: symbolsStream,
                embeddedTexts: embeddedTexts,
                options: emitOptions);


            if (result.Success)
            {
               Console.WriteLine("Complation succeeded!");
               try
               {
                  Assembly nugetAssembly = Assembly.LoadFrom(pathToNugetDLL);

                  var assembly = Assembly.Load(assemblyStream.ToArray(), symbolsStream.ToArray());
                  var type = assembly.GetType("A.MyClass");

                  MethodInfo method = type.GetMethod("MyFunction");

                  var fooInstance = Activator.CreateInstance(type);
                  method.Invoke(fooInstance, null);
                  
               }
               catch (Exception ex)
               {
                  int i = 0;
               }
            }
         }
      }
      private static List<MetadataReference> CreateMetadataReferences()
      {
         string defaultPath = typeof(object).Assembly.Location.Replace("mscorlib", "{0}");

         var metadatenReferences = new List<MetadataReference>()
            {
                MetadataReference.CreateFromFile(string.Format(defaultPath, "mscorlib")),
                MetadataReference.CreateFromFile(string.Format(defaultPath, "System")),
                MetadataReference.CreateFromFile(string.Format(defaultPath, "System.Data")),
                MetadataReference.CreateFromFile(string.Format(defaultPath, "System.Core")),
                MetadataReference.CreateFromFile(string.Format(defaultPath, "System.ComponentModel.DataAnnotations")),
                MetadataReference.CreateFromFile(string.Format(defaultPath, "System.Xml")),
                MetadataReference.CreateFromFile(string.Format(defaultPath, "netstandard")),
            };

         string strExtraDll = pathToNugetDLL;
         metadatenReferences.Add(MetadataReference.CreateFromFile(strExtraDll));

         return metadatenReferences;
      }
   }
         
}

You're, maybe, missing loading the dependencies of TinyCsvParser. Try creating a project with that same code you're trying to compile and see what assemblies are referenced. — Paulo Morgado, Jul 15 '21 at 17:15

MarkusE · Accepted Answer · 2021-07-20T14:05:02.140

I could solve the problem by using the event Handler

AppDomain.CurrentDomain.AssemblyResolve

With it i could resolve the Dependency.

Here the final result of the prototype code:

using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.Emit;
using Microsoft.CodeAnalysis.Text;
using System;
using System.Collections.Generic;
using System.IO;
using System.Reflection;
using System.Text;
using System.Text.RegularExpressions;

namespace Playground
{
   public static class Program
   {

      public static void Main()
      {
         var test = new Test();
         test.TestMethod();
      }
   }
   public class Test

   {

      private const string pathToNugetDLL = @"C:\Data\packages\tinycsvparser.2.6.1\lib\net45\TinyCsvParser.dll";

      private const string firstClass =
@"
using TinyCsvParser;

namespace A
{
    public class MyClass
    {
        public int MyFunction()
         {
            CsvParserOptions csvParserOptions = new CsvParserOptions(true, ';');
            return 1;
         }
    }
}";


      public void TestMethod()
      {
         CSharpParseOptions parseOptions = new CSharpParseOptions(LanguageVersion.CSharp7, DocumentationMode.Parse, SourceCodeKind.Regular);
         SyntaxTree parsedSyntaxTree = SyntaxFactory.ParseSyntaxTree(firstClass, parseOptions);

         List<string> defaultNamespaces = new List<string>() { };

         //// Referenzen über Kommentare heraussuchen:
         List<MetadataReference> defaultReferences = CreateMetadataReferences();

         var encoding = Encoding.UTF8;

         var assemblyName = Path.GetRandomFileName();
         var symbolsName = Path.ChangeExtension(assemblyName, "pdb");
         var sourceCodePath = "generated.cs";

         var buffer = encoding.GetBytes(firstClass);
         var sourceText = SourceText.From(buffer, buffer.Length, encoding, canBeEmbedded: true);

         var syntaxTree = CSharpSyntaxTree.ParseText(
             sourceText,
             new CSharpParseOptions(),
             path: sourceCodePath);

         var syntaxRootNode = syntaxTree.GetRoot() as CSharpSyntaxNode;
         var encoded = CSharpSyntaxTree.Create(syntaxRootNode, null, sourceCodePath, encoding);


         CSharpCompilationOptions defaultCompilationOptions =
               new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
                       .WithOverflowChecks(true).WithOptimizationLevel(OptimizationLevel.Debug).WithPlatform(Platform.AnyCpu)
                       .WithUsings(defaultNamespaces);

         CSharpCompilation compilation = CSharpCompilation.Create(
             assemblyName,
             syntaxTrees: new[] { encoded },
             references: defaultReferences,

             options: defaultCompilationOptions
         );

         using (var assemblyStream = new MemoryStream())
         using (var symbolsStream = new MemoryStream())
         {
            var emitOptions = new EmitOptions(
                    debugInformationFormat: DebugInformationFormat.Pdb,
                    pdbFilePath: symbolsName);

            var embeddedTexts = new List<EmbeddedText> { EmbeddedText.FromSource(sourceCodePath, sourceText) };

            EmitResult result = compilation.Emit(
                peStream: assemblyStream,
                pdbStream: symbolsStream,
                embeddedTexts: embeddedTexts,
                options: emitOptions);


            if (result.Success)
            {
               Console.WriteLine("Complation succeeded!");
               try
               {
                  AppDomain.CurrentDomain.AssemblyResolve += AppDomain_AssemblyResolve;

                  Assembly nugetAssembly = Assembly.LoadFrom(pathToNugetDLL);

                  var assembly = Assembly.Load(assemblyStream.ToArray(), symbolsStream.ToArray());
                  var type = assembly.GetType("A.MyClass");

                  MethodInfo method = type.GetMethod("MyFunction");

                  var fooInstance = Activator.CreateInstance(type);
                  method.Invoke(fooInstance, null);

               }
               catch (Exception ex)
               {
                  int i = 0;
               }
               finally
               {
                  AppDomain.CurrentDomain.AssemblyResolve -= AppDomain_AssemblyResolve;
               }
            }
         }
      }


      private Assembly AppDomain_AssemblyResolve(object sender, ResolveEventArgs args)
      {
         string[] assemblyInfoSplitted = args.Name.Split(',');
         string strSearchedForAssemblyName = assemblyInfoSplitted[0];

         var fileInfo = new FileInfo(pathToNugetDLL);
         var strAssemblyName = Regex.Replace(fileInfo.Name, ".dll", "", RegexOptions.IgnoreCase);
         if (strSearchedForAssemblyName.ToLower() == strAssemblyName.ToLower())
         {
            //File.ReadAllBytes because DLL might be deleted afterwards in the filesystem
            return Assembly.Load(File.ReadAllBytes(pathToNugetDLL));
         }

         throw new Exception($"Could not resolve Assembly '{strSearchedForAssemblyName}'.");
      }

      private static List<MetadataReference> CreateMetadataReferences()
      {
         string defaultPath = typeof(object).Assembly.Location.Replace("mscorlib", "{0}");

         var metadatenReferences = new List<MetadataReference>()
            {
                MetadataReference.CreateFromFile(string.Format(defaultPath, "mscorlib")),
                MetadataReference.CreateFromFile(string.Format(defaultPath, "System")),
                MetadataReference.CreateFromFile(string.Format(defaultPath, "System.Data")),
                MetadataReference.CreateFromFile(string.Format(defaultPath, "System.Core")),
                MetadataReference.CreateFromFile(string.Format(defaultPath, "System.ComponentModel.DataAnnotations")),
                MetadataReference.CreateFromFile(string.Format(defaultPath, "System.Xml")),
                MetadataReference.CreateFromFile(string.Format(defaultPath, "netstandard")),
            };

         string strExtraDll = pathToNugetDLL;
         metadatenReferences.Add(MetadataReference.CreateFromFile(strExtraDll));

         return metadatenReferences;
      }
   }

}

@PauloMorgado : I Just added the complete code with event handler. — MarkusE, Jul 19 '21 at 06:27
https://stackoverflow.com/a/41697292/3405498 explains why File.ReadAllBytes is used with Assembly.Load — MarkusE, Jul 20 '21 at 14:05

score 1 · Answer 2 · answered Jul 19 '21 at 10:30

You have 2 issues here:

Compiling
Running

Try this:

public class Test
{
    private const string firstClass =
@"
using TinyCsvParser;

namespace A
{
    public class MyClass
    {
        public int MyFunction()
         {
            CsvParserOptions csvParserOptions = new CsvParserOptions(true, ';');
            return 1;
         }
    }
}";


    public void TestMethod()
    {
        var parseOptions = new CSharpParseOptions(LanguageVersion.CSharp7, DocumentationMode.Parse, SourceCodeKind.Regular);
        var parsedSyntaxTree = SyntaxFactory.ParseSyntaxTree(firstClass, parseOptions);

        var defaultReferences = CreateMetadataReferences();

        var encoding = Encoding.UTF8;

        var assemblyName = Path.GetRandomFileName();
        var symbolsName = Path.ChangeExtension(assemblyName, "pdb");
        var sourceCodePath = "generated.cs";

        var buffer = encoding.GetBytes(firstClass);
        var sourceText = SourceText.From(buffer, buffer.Length, encoding, canBeEmbedded: true);

        var syntaxTree = CSharpSyntaxTree.ParseText(
            sourceText,
            new CSharpParseOptions(),
            path: sourceCodePath);

        var syntaxRootNode = syntaxTree.GetRoot() as CSharpSyntaxNode;
        var encoded = CSharpSyntaxTree.Create(syntaxRootNode, null, sourceCodePath, encoding);

        CSharpCompilationOptions defaultCompilationOptions =
              new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
                  .WithOverflowChecks(true)
                  .WithOptimizationLevel(OptimizationLevel.Debug)
                  .WithPlatform(Platform.AnyCpu);

        CSharpCompilation compilation = CSharpCompilation.Create(
            assemblyName,
            syntaxTrees: new[] { encoded },
            references: defaultReferences,

            options: defaultCompilationOptions
        );

        using var assemblyStream = new MemoryStream();
        using var symbolsStream = new MemoryStream();

        var emitOptions = new EmitOptions(
                debugInformationFormat: DebugInformationFormat.Pdb,
                pdbFilePath: symbolsName);

        var embeddedTexts = new List<EmbeddedText> { EmbeddedText.FromSource(sourceCodePath, sourceText) };

        EmitResult result = compilation.Emit(
            peStream: assemblyStream,
            pdbStream: symbolsStream,
            embeddedTexts: embeddedTexts,
            options: emitOptions);

        if (result.Success)
        {
            Console.WriteLine("Complation succeeded!");

            try
            {
                var assembly = Assembly.Load(assemblyStream.ToArray(), symbolsStream.ToArray());
                var type = assembly.GetType("A.MyClass");

                MethodInfo method = type.GetMethod("MyFunction");

                var fooInstance = Activator.CreateInstance(type);
                method.Invoke(fooInstance, null);

                Console.WriteLine("Invocation succeeded!");
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Invocation failed!\n{ex}");
            }
        }
        else
        {
            Console.WriteLine("Complation failed!");

            foreach (var diagnostic in result.Diagnostics)
            {
                Console.WriteLine(diagnostic.ToString());
            }
        }
    }

    private static IEnumerable<MetadataReference> CreateMetadataReferences()
    {
        var tinyCsvParserAssembly = typeof(TinyCsvParser.CsvParserOptions).Assembly;

        var metadatenReferences = new Dictionary<string, MetadataReference>();

        GetReferenecedAssemblies(metadatenReferences, tinyCsvParserAssembly);

        return metadatenReferences.Values;

        static void GetReferenecedAssemblies(Dictionary<string, MetadataReference> references, Assembly assembly)
        {
            var assemblyName = assembly.FullName;

            if (!references.ContainsKey(assemblyName))
            {
                references.Add(assemblyName, MetadataReference.CreateFromFile(assembly.Location));

                foreach (var referencedAssembly in assembly.GetReferencedAssemblies())
                {
                    GetReferenecedAssemblies(references, Assembly.Load(referencedAssembly));
                }
            }
        }
    }
}

Thank you for the effort. But this only works when the Nuget is already referenced in the calling assembly. In my case this is not the case. — MarkusE, Jul 20 '21 at 14:07
This answer was based on your question and answer, It you can resolve the assembly on the same process, you can compile with those references. — Paulo Morgado, Jul 20 '21 at 14:39
NuGet packages are not referenced by the code/compiler. NuGet contain assemblies that are referenced by the code/compiler. NuGet packages are referenced by the project system. — Paulo Morgado, Jul 20 '21 at 14:40
That's right. I meant the assembly within the Nuget-Package. I should have distinguished that. My wording was not right here. — MarkusE, Jul 20 '21 at 14:46

C# Roslyn Compile - Use Nuget Package within dynamically compiled Code - compiles but throws an Exception at runtime (Could not load file or assembly)

2 Answers2