Roslyn Scripting Emit Compilation

So far, we have discussed how to evaluate, analyze and manipulate source code. Now let's have a look at how to emit the compilation of your source code. You can emit it to either disk or memory.

The following example emits the source code to the output.exe file.

static void EmitCompilationExample()
{
    SyntaxTree tree = CSharpSyntaxTree.ParseText(
        @"using System;
        using System.Collections;
        using System.Text;
         
        namespace HelloWorld
        {
            class Program
            {
                static void Main(string[] args)
                {
                    Console.WriteLine(""Hello, World!"");
                }
            }
        }");

    var mscorlib = MetadataReference.CreateFromFile(typeof(object).Assembly.Location);

    var compilation = CSharpCompilation.Create("MyCompilation",
        syntaxTrees: new[] { tree }, references: new[] { mscorlib });

    var emitResult = compilation.Emit("output.exe", "output.pdb");

    if (!emitResult.Success)
    {
        foreach (var diagnostic in emitResult.Diagnostics)
        {
            Console.WriteLine(diagnostic.ToString());
        }
    }
}

Let's execute the above code, and you will see that the .exe and .pdb files have been emitted to Debug/bin/.

You can also emit the compilation of the source code to the memory and then execute it from memory, as shown below.

static void EmitCompilationToMemoryExample()
{
    SyntaxTree tree = CSharpSyntaxTree.ParseText(
        @"using System;
        using System.Collections;
        using System.Text;
         
        namespace HelloWorld
        {
            class Program
            {
                static void Main(string[] args)
                {
                    Console.WriteLine(""Hello, World!"");
                }
            }
        }");

    var mscorlib = MetadataReference.CreateFromFile(typeof(object).Assembly.Location);

    var compilation = CSharpCompilation.Create("MyCompilation",
        syntaxTrees: new[] { tree }, references: new[] { mscorlib });

    var ms = new MemoryStream();
    var emitResult = compilation.Emit(ms);

    var ourAssembly = Assembly.Load(ms.ToArray());
    var type = ourAssembly.GetType("Program");

    type.InvokeMember("Main", BindingFlags.Default | BindingFlags.InvokeMethod, null, null, null);
}