Cannot compile simple dynamic code after migration on .netstandard 2.0 (CodeDom throws System.PlatformNotSupportedException)

Question

Trying to compile this sample of code:

var c = new CSharpCodeProvider();
var cp = new CompilerParameters();
var className = $"CodeEvaler_{Guid.NewGuid().ToString("N")}";
// doesn't work with or without netstandard reference
var netstandard = Assembly.Load("netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51");
cp.ReferencedAssemblies.Add(netstandard.Location);
cp.CompilerOptions = "/t:library";
cp.GenerateInMemory = true;

var sb = new StringBuilder("");

sb.Append("namespace Jobs.Dynamic{ \n");
sb.Append($"public class {className} {{\n");
sb.Append($"public object RunSnippetCode()\n{{\n");
sb.Append("\nreturn null;\n");
sb.Append("\n}\n");
sb.Append("}");
sb.Append("}");

CompilerResults cr = c.CompileAssemblyFromSource(cp, sb.ToString());

Everything was ok before migration on .netstandard 2.0

A simple class has to be generated and it works if just copy the code and run it in Visual Studio. The class with one method that returns null. Now CompileAssemblyFromSource method throws

System.PlatformNotSupportedException: Operation is not supported on this platform. at Microsoft.CSharp.CSharpCodeGenerator.FromFileBatch(CompilerParameters options, String[] fileNames) at Microsoft.CSharp.CSharpCodeGenerator.System.CodeDom.Compiler.ICodeCompiler.CompileAssemblyFromSourceBatch(CompilerParameters options, String[] sources) at CnetContent.Jobs.DynamicCode..ctor(IEnumerable1 referencedAssemblies, IEnumerable1 usings, String methodArgs, String codeSnippet) at CnetContent.Jobs.Core.JobBase.EvalRunCondition(String& error)

I updated System.CodeDom and this library supports .netstandard 2.0, but this code still doesn't work. Could not find any cases with similar problems. Any ideas? Thank you in advance!

Answer 1

In my case I was migrating a project from .NET Framework 4.7.2 to .NET Standard 2.0. In this project I have code to generate an assembly during runtime by using CSharpCodeProvider. Could compile the project but then during runtime my code threw an exception when generating an assembly from Dom. I got this error:

CS0012: The type 'System.Object' is defined in an assembly that is not referenced. You must add a reference to assembly 'netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'.

As a consequence the assembly was not created during runtime.

In order to fix that I have added .netstandard for the compiler as a referenced assembly like that:

var compilerParameters = new CompilerParameters();
var netstandard = Assembly.Load("netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51");
compilerParameters.ReferencedAssemblies.Add(netstandard.Location);

That did the trick for me.

Answer 2

I had the same problem with .NetCore 2, but with a bigger CodeDOM project. My solution I am right now building is generating the source from CodeDom and then passing it to Roslyn. (As Roslyn was mentioned in a comment, but only a .NET Framwork solution was posted)

Here is a good example how to use Roslyn - just add the

Microsoft.CodeAnalysis.CSharp NuGet package and System.Runtime.Loader NuGet package

and then use the code here (Or just follow the example): https://github.com/joelmartinez/dotnet-core-roslyn-sample/blob/master/Program.cs