Roslyn is the new open source .NET compiler platform from Microsoft that provides APIs to build code analysis tools. It treats the compiler as a service by exposing the compile pipeline. Developers can get started with Roslyn by downloading the SDK, installing Visual Studio extensions, and using project templates to build console apps, diagnostics, or code fixes that interface with the compiler at different stages. Existing projects like ScriptCS demonstrate early uses of Roslyn.

1. ROSLYN
What it is and how to get started
Oslo/NNUG
Tomas Jansson
27/05/2014

2. THIS IS ME
Tomas Jansson
Manager & Practice Lead .NET
BEKK Oslo
@TomasJansson
tomas.jansson@bekk.no
github.com/mastoj
blog.tomasjansson.com

3. AGENDA
What is Roslyn
Summary
The compile
pipeline
How to get
started
Existing projectsDemo

4. WHAT IS ROSLYN?
The .NET Compiler Platform ("Roslyn") provides open-source
C# and Visual Basic compilers with rich code analysis APIs.
You can build code analysis tools with the same APIs that
Microsoft is using to implement Visual Studio!
http://roslyn.codeplex.com/

5. WHAT IS ROSLYN?
The .NET Compiler Platform ("Roslyn") provides open-source
C# and Visual Basic compilers with rich code analysis APIs.
You can build code analysis tools with the same APIs that
Microsoft is using to implement Visual Studio!
http://roslyn.codeplex.com/

6. WHAT IS ROSLYN?
It’s a ”compiler-as-a-service (caas)”

7. WHAT IS A COMPILER-AS-A-SERVICE?
”C# compiler is like a box of chocolates,
you never know what you’re gonna get”
http://theawesomedaily.theawesomedaily.netdna-cdn.com/wp-content/uploads/2013/12/forrest-gump-original.jpeg

8. WHAT IS A COMPILER-AS-A-SERVICE?
”C# compiler is like a box of chocolates,
you never know what you’re gonna get”
This was life
before Roslyn
http://theawesomedaily.theawesomedaily.netdna-cdn.com/wp-content/uploads/2013/12/forrest-gump-original.jpeg

9. Now we know
exactly what
we gonna get!

10. WHY?
Power to the
developers
Easier to add
features (for
Microsoft)

11. THE COMPILE PIPELINE
http://roslyn.codeplex.com/wikipage?title=Overview&referringTitle=Home

12. HOW TO GET STARTED
Download and install the SDK: http://roslyn.codeplex.com/
Run ”Install Roslyn Preview into Roslyn Experimental Hive.exe”
Install all the Visual Studio Extensions
Roslyn End User Preview.vsix
Roslyn SDK Project Templates.vsix
Roslyn Syntax Visualizer.vsix

13. HOW TO GET STARTED
Download and install the SDK: http://roslyn.codeplex.com/
Run ”Install Roslyn Preview into Roslyn Experimental Hive.exe”
Install all the Visual Studio Extensions
Roslyn End User Preview.vsix
Roslyn SDK Project Templates.vsix
Roslyn Syntax Visualizer.vsix
Important to run
the .exe first and
then the vsix files

14. PROJECT TEMPLATES

15. PROJECT TEMPLATES
Console
applications
Create code
refactoring
plugins
Diagnostic,
build
extensions

16. SYNTAX VISUALIZER

17. DEMO
https://github.com/mastoj/RoslynSamples

18. KEY PARTS: CONSOLE APPLICATION
Install-package -pre Microsoft.CodeAnalysis.Csharp
// Create the syntax tree
var syntaxTree = CSharpSyntaxTree.ParseText(code);
// Compile the syntax tree
var compilation = CSharpCompilation.Create("Executable", new[] {syntaxTree},
_defaultReferences,
new CSharpCompilationOptions(OutputKind.ConsoleApplication));
private static IEnumerable<string> _defaultReferencesNames =
new [] { "mscorlib.dll", "System.dll", "System.Core.dll" };
private static string _assemblyPath =
Path.GetDirectoryName(typeof(object).Assembly.Location);
private static IEnumerable<MetadataFileReference> _defaultReferences =
_defaultReferencesNames.Select(
y => new MetadataFileReference(Path.Combine(_assemblyPath, y)));

19. KEY PARTS: CONSOLE APPLICATION
private Assembly CreateAssembly(CSharpCompilation compilation)
{
using(var outputStream = new MemoryStream())
using (var pdbStream = new MemoryStream())
{
// Emit assembly to streams
var result = compilation.Emit(outputStream, pdbStream: pdbStream);
if (!result.Success)
{
throw new CompilationException(result);
}
// Load the compiled assembly;
var assembly = Assembly.Load(outputStream.ToArray(), pdbStream.ToArray());
return assembly;
}
}
// Execute the assembly
assembly.EntryPoint.Invoke(null, new object[] { args });

20. KEY PARTS: DIAGNOSIS (DIAGNOSTIC ANALYZER)
Use project template: Diagnosis with Code Fix
public class DiagnosticAnalyzer : ISyntaxNodeAnalyzer<SyntaxKind>
public ImmutableArray<SyntaxKind> SyntaxKindsOfInterest
{
get { return ImmutableArray.Create(SyntaxKind.IfStatement); }
}
public void AnalyzeNode(SyntaxNode node, SemanticModel semanticModel,
Action<Diagnostic> addDiagnostic, CancellationToken cancellationToken)
What type analysis do
we want?
What kind of syntax
are we interested in?
Analyze and add
diagnostic.

21. KEY PARTS: DIAGNOSIS (CODE FIX PROVIDER)
public async Task<IEnumerable<CodeAction>> GetFixesAsync(Document document,
TextSpan span, IEnumerable<Diagnostic> diagnostics,
CancellationToken cancellationToken)
{
// Get the syntax root
var root = await document.GetSyntaxRootAsync(cancellationToken);
// Find the token that triggered the fix
var token = root.FindToken(span.Start);
if (token.IsKind(SyntaxKind.IfKeyword))
{
// Find the statement you want to change
var ifStatment = (IfStatementSyntax)token.Parent;
// Create replacement statement
var newIfStatement = ifStatment
.WithStatement(SyntaxFactory.Block(ifStatment.Statement))
.WithAdditionalAnnotations(Formatter.Annotation);
// New root based on the old one
var newRoot = root.ReplaceNode(ifStatment, newIfStatement);
return new[] {CodeAction.Create("Add braces",
document.WithSyntaxRoot(newRoot))};
}
return null;
}

22. EXISTING PROJECTS
ScriptCS
Build using the scripting engine in the CTP
Script engine is not available in the User Preview, but it will come back at some point

23. EXISTING PROJECTS
ScriptCS
Build using the scripting engine in the CTP
Script engine is not available in the User Preview, but it will come back at some point
Great for
exploration

24. SUMMARY
Roslyn is the new C# compiler from Microsoft
It’s open source
It’s a compiler-as-a-service
The have made easy to use project templates to extend Visual studio

25. RESOURCES
Good example blog post: http://tinyurl.com/RoslynExample
The Roslyn project: http://roslyn.codeplex.com/
Syntax Visualizer Overview: http://tinyurl.com/RoslynVisualizer
Source code to my demos: https://github.com/mastoj/RoslynSamples
Presentation from BUILD 2014: http://channel9.msdn.com/Events/Build/2014/2-577
My presentation on Slideshare: http://tinyurl.com/123Roslyn

26. Thank you!
@TomasJansson