What is Roslyn and how can we use it? Telerik Academy Plus C# 6.0 and Roslyn Seminar

 What is "Roslyn"?  Exposing the compiler  Pipeline  API layer  Working with syntax  Trees, Nodes, Tokens, Trivia  Semantics  Compilation  Semantic model 2

.NET Compiler Platform

 Normal compiler – traditionally black box  Source code in  Magic in between  Assemblies out  Nowadays we use  Intellisense  Refactoring  Code productivity tools 4

 Traditional compiler pipeline  Parser – parses text to syntax objects  Symbols/Metadata – declarations are collected  Binder – identifiers, code flow bind to symbols  IL Emitter – IL assembly creation 5

 Each phase now has corresponding API 6

The Grammar Nazi of Programming

 Why – without text processing tools can:  See the structure of the source code  Create and rearrange source code  Contains  Syntax Trees  Syntax Nodes  Syntax Tokens  Syntax Trivia  Spans and Kinds 8

 Syntax Trees  Primary structure for compilation  Hold all the source information  Constructs  Tokens  Everything!  Two-way communication with the source text  Immutable and thread-safe  Contains Nodes, Tokens, Trivia 9

 Syntax Trees  Useful members  GetRoot()  GetText()  GetChanges()  Options 10 var code = File.ReadAllText("Code.cs"); var tree = SyntaxFactory.ParseSyntaxTree(code);

 Syntax Nodes  Primary element of Syntax Tree  Represents  Declarations  Statements  Clauses  Expressions  Each node has children – other nodes and tokens 11

 Syntax Nodes  Useful members  Modifiers  Type  Parent  DescendantNodes() 12 var localDeclarationNodes = tree.GetRoot().DescendantNodes().DescendantNodes().OfType ();.OfType ();

 Syntax Tokens  Smallest syntactic fragment – no children  Represents  Keywords  Identifiers  Literals  Punctuation 13 var tokens = node.ChildTokens(); var token = tokens.First(); token.Value;

 Syntax Trivia  Whitespace, comments, etc.  Spans  Position and number of characters within the source code  Kinds  Identifies the exact syntax element represented  Errors  Missing tokens or skipped tokens 14

Let's build something

 Compilation needs  Syntax Tree  Compilation Options  File Reference 16 var options = new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary); var reference = new MetadataFileReference(typeof(object).Assembly.Location); var compilation = CSharpCompilation.Create("Test").WithOptions(options).WithOptions(options).AddSyntaxTrees(tree).AddSyntaxTrees(tree).AddReferences(reference);.AddReferences(reference);

 Additional semantic information for source code  Symbols at specific location  Resultant type of any expression  Errors and warnings  Variable flow in and out of source parts  Answer to everything – 42? 17

 Semantic Model 18 var comp = CreateCompilation(tree, options, reference); var model = comp.GetSemanticModel(tree); var localDeclarationNodes = tree.GetRoot().DescendantNodes().DescendantNodes().OfType ();.OfType (); foreach (var node in localDeclarationNodes) { var info = model.GetTypeInfo(node.Declaration.Type); var info = model.GetTypeInfo(node.Declaration.Type); Console.WriteLine("{0} {1}", info.Type, node.Declaration); Console.WriteLine("{0} {1}", info.Type, node.Declaration);}

Actually use the code

 Using the dynamically compiled result  Emit to memory stream  Load assembly from byte array  Use with normal reflection 20 using (var memory = new MemoryStream()) { compilation.Emit(memory); compilation.Emit(memory); var assembly = Assembly.Load(memory.GetBuffer()); var assembly = Assembly.Load(memory.GetBuffer()); var type = assembly.GetType("NameOfType"); var type = assembly.GetType("NameOfType"); var instance = Activator.CreateInstance(type); var instance = Activator.CreateInstance(type);}

Live Demo

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