Loading an assembly generated by the Roslyn compiler

Question

I\'m generating a Greeter.dll using the Roslyn compiler. My problem occurs trying to load the DLL file.

Here\'s the code:

using System;

using Rosly         


        

Answer 1

I stumbled across this and, even though you have an accepted answer, I don't think it's helpful in general. So, I'll just leave this here for future searchers like myself.

The problem with the code is two things, which you would have found out by looking at the returned value from

EmitResult result = compilation.Emit(file);

If you look at the properties on the EmitResult object, you would have found that there were 2 errors in the results.Diagnostics member.

1. Main method not found
2. Couldn't find class Console

So, to fix the problem, 1. You need to mark the output as a dll 2. You need to add 'using System;' to the code you're passing into the API or say 'System.Console.WriteLine'

The following code works making changes to fix those two issues:

        var outputFile = "Greeter.dll";
        var syntaxTree = SyntaxTree.ParseCompilationUnit(@"
 // ADDED THE FOLLOWING LINE
using System;

class Greeter
{
    public void Greet()
    {
        Console.WriteLine(""Hello, World"");
    }
}");
        var compilation = Compilation.Create(outputFile,
            syntaxTrees: new[] { syntaxTree },
            references: new[] {
                new AssemblyFileReference(typeof(object).Assembly.Location),
                new AssemblyFileReference(typeof(Enumerable).Assembly.Location),
            },

// ADDED THE FOLLOWING LINE
            options: new CompilationOptions(OutputKind.DynamicallyLinkedLibrary));

        using (var file = new FileStream(outputFile, FileMode.Create))
        {
            EmitResult result = compilation.Emit(file);
        }

        Assembly assembly = Assembly.LoadFrom("Greeter.dll");

        Type type = assembly.GetType("Greeter");
        var obj = Activator.CreateInstance(type);

        type.InvokeMember("Greet",
            BindingFlags.Default | BindingFlags.InvokeMethod,
            null,
            obj,
            null);

        Console.WriteLine(" to continue");
        Console.ReadLine();