Compiling and Running code at runtime in .Net Core 1.0

Question

Is it possible to compile and run C# code at runtime in the new .Net Core (better .Net Standard Platform)? I have seen some examples (.Net Framework), but they used NuGet pa

Answer 1

Just adding to @svick option one answer. If you want to keep the assembly in memory (rather than writing to a file) you can use the following method:

AssemblyLoadContext context = AssemblyLoadContext.Default;
Assembly assembly = context.LoadFromStream(ms);

This is different that in Net451 where the code is:

Assembly assembly = Assembly.Load(ms.ToArray());

My code targets both Net451 and Netstandard so I had to use directives to get around this problem. The full code example is here:

                   string code = CreateFunctionCode();
                    var syntaxTree = CSharpSyntaxTree.ParseText(code);

                    MetadataReference[] references = new MetadataReference[]
                    {
                        MetadataReference.CreateFromFile(typeof(object).GetTypeInfo().Assembly.Location),
                        MetadataReference.CreateFromFile(typeof(Hashtable).GetTypeInfo().Assembly.Location)
                    }; 

                     var compilation = CSharpCompilation.Create("Function.dll",
                        syntaxTrees: new[] { syntaxTree },
                        references: references,
                        options: new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary));

                    StringBuilder message = new StringBuilder();

                    using (var ms = new MemoryStream())
                    {
                        EmitResult result = compilation.Emit(ms);

                        if (!result.Success)
                        {
                            IEnumerable failures = result.Diagnostics.Where(diagnostic =>
                                diagnostic.IsWarningAsError ||
                                diagnostic.Severity == DiagnosticSeverity.Error);

                            foreach (Diagnostic diagnostic in failures)
                            {
                                message.AppendFormat("{0}: {1}", diagnostic.Id, diagnostic.GetMessage());
                            }

                            return new ReturnValue(false, "The following compile errors were encountered: " + message.ToString(), null);
                        }
                        else
                        {

                            ms.Seek(0, SeekOrigin.Begin);

 #if NET451
                            Assembly assembly = Assembly.Load(ms.ToArray());
 #else
                            AssemblyLoadContext context = AssemblyLoadContext.Default;
                            Assembly assembly = context.LoadFromStream(ms);
 #endif

                            Type mappingFunction = assembly.GetType("Program");
                            _functionMethod = mappingFunction.GetMethod("CustomFunction");
                            _resetMethod = mappingFunction.GetMethod("Reset");
                        }
                    }