cfg-compile.cs

static Compilation Compile(string code)
{
    var parserOptions = new CSharpParseOptions(languageVersion: LanguageVersion.CSharp7);
    var parsedTree = CSharpSyntaxTree.ParseText(code, options: parserOptions);

    //Assert parser success
    Debug.Assert(!parsedTree.GetRoot().HasErrors());

    //Enable flow-analysis feature flag
    var options = parsedTree.Options.WithFeatures(new[] { new KeyValuePair<string, string>("flow-analysis", "true") });
    parsedTree = parsedTree.WithRootAndOptions(parsedTree.GetRoot(), options);

    //Compile and link with. mscorlib.dll
    var mscorlib = MetadataReference.CreateFromFile(typeof(object).Assembly.Location);
    var compilation = CSharpCompilation.Create("MyCompilation",
        syntaxTrees: new[] { parsedTree }, 
        references: new[] { mscorlib });

    return compilation;
}

static ControlFlowGraph GetTreeCFG(Compilation compilation)
{
    var tree = compilation.SyntaxTrees.Single();

    var root = tree.GetRoot();

    var semanticModel = compilation.GetSemanticModel(tree);
    var firstMethod = root.DescendantNodes().OfType<BaseMethodDeclarationSyntax>().First();
    var firstMethodOper = semanticModel.GetOperation(firstMethod) as IMethodBodyOperation;

    return ControlFlowGraph.Create(firstMethodOper);
}