The document discusses reflection in .NET, which allows examining and modifying programs at runtime. Reflection provides objects that encapsulate metadata about types and members. It allows dynamically creating instances, invoking methods, and accessing fields and properties. The System.Reflection and System.Reflection.Emit namespaces contain classes for reading and modifying metadata.

2. Understanding Reflection Tamir Khason Technology Consultor ¹ mPrest Systems http://blogs.microsoft.co.il/blogs/tamir Session Code: DVP307 ¹ con·sul·tor (kən sult ′ ər) - one of a group of priests appointed to advise and assist a bishop

3. CLR – compilation and execution Execution Compilation Source code Language compiler JIT compiler Before installation or the first time each method is called MSIL Metadata Code Native code

4. Reflection overview All types in the CLR are self-describing CLR provides a reader and writer for type definitions System.Reflection & System.Reflection.emit You can ‘read’ programs You can map between type systems You can interrogate objects and types inside a running program

5. What is “Reflection”? “ Reflection provides objects that encapsulate assemblies, modules, and types. ” (MSDN) “ You can use reflection to dynamically create an instance of a type... ” (MSDN) “ You can then invoke the type's methods or access its fields and properties. ” (MSDN) “ Reflection.Emit namespace contains classes that allow a compiler or tool to emit metadata and Microsoft intermediate language (MSIL) ” (MSDN)

6. Where is “Reflection”? System.Reflection namespace contains most Reflection classes. System.Type is Reflection class used to access type metadata. … more…

7. How to “Reflection”? Viewing metadata Performing type discovery Late binding to methods and properties (Dynamic Invocation) Creating types at runtime (Reflection Emit)

8. How to… perform type discovery You can use reflection to explore and examine the contents of an assembly programmatically You can find methods, fields, properties, and events associated with a type signatures of each of the type's methods; interfaces supported by the type; type's base class. …

9. What are you? Value, Interface or Class? IsValueType, IsInterface, IsClass Public, Private or Sealed ? IsNotPublic, IsSealed Abstract or Implementation? IsAbstract

10. What you have? Finding and Exploring Members MemberInfo: GetMembers(), FindMembers() Exploring Fields and Properties FieldInfo: GetFields(), PropertyInfo: GetProperties() Exploring Constructors, Methods and Events GetConstructors(), GetMethods(), GetEvents() Exploring attributes, determining implemented interfaces, enumerating nested types, … Everything you may ever want to know

11. MemberInfo Base class for all "member" element descriptions Fields, Properties, Methods, etc. Provides member kind, name and declaring class MemberInfo MethodBase ParameterInfo FieldInfo EventInfo PropertyInfo MethodInfo ConstructorInfo

12. MethodInfo vs. ConstructorInfo MethodInfo Return type and attributes List of all parameters as ParameterInfo array Detail implementation information through flag-field Can invoke method through Reflection ConstructorInfo Same features as MethodInfo, just for constructors

13. FieldInfo vs. PropertyInfo FieldInfo Field data type and attributes Static or Instance field, protection level Can set value through reflection Provides low-level, direct access with SetValueDirect() PropertyInfo Property type and attributes Test methods for readability, writeability "get" and "set" MethodInfo Indexer ParameterInfo Can invoke "set" and "get" through Reflection

14. We can clone it… Type kidType = oldKid.GetType(); Kid newKid = new Kid(); foreach (var m in kidType.GetProperties()) { m.SetValue(newKid , m.GetValue(oldKid, null), null); } Unknown object GetType().GetMembers() For Each Member FieldInfo.Copy old value to new Object

15. Clone optimization Kid CloneKid(Kid) { newKid.Height = oldKid.Height newKid.Weight = oldKid.Weight } Unknown object GetType().GetMembers() For Each Member Create Code that copies members Save as Method for later Invocation

16. Clone optimized Unknown object Has custom method? Execute Yes Copy Members No

17. What is… attributes An attribute is an object that represents data you want to associate with an element in your program. Two Kinds of Attributes: Intrinsic : Supplied as part of the Common Language Runtime (CLR) Custom : Attributes you create for your own purposes

18. Code generation Using Dynamic Invoke Create and compile source code in runtime Persistent in disk Invoke Compiler to generate IL Using Reflection Emit Emit IL code directly Temporarily stored in memory Better performance Kid CloneKid(Kid) { newKid.Height = oldKid.Height newKid.Weight = oldKid.Weight }

20. CodeDOM CodeEntryPointMethod start = new CodeEntryPointMethod(); CodeMethodInvokeExpression cs1 = new CodeMethodInvokeExpression( new CodeTypeReferenceExpression ("System.Console"), "WriteLine", new CodePrimitiveExpression ("Hello World!") ); start.Statements.Add(cs1); public static void Main() { System.Console.WriteLine(“Hello World!”); }

21. CodeDOM CodeArgumentReferenceExpression CodeArrayCreateExpression CodeArrayIndexerExpression CodeAssignStatement CodeAttachEventStatement CodeAttributeArgument CodeAttributeArgumentCollection CodeAttributeDeclaration CodeAttributeDeclarationCollection CodeBaseReferenceExpression CodeBinaryOperatorExpression CodeCastExpression CodeCatchClause CodeCatchClauseCollection CodeComment CodeCommentStatement CodeCommentStatementCollection CodeCompileUnit CodeConditionStatement CodeConstructor CodeDelegateCreateExpression CodeExpressionCollection CodeExpressionStatement CodeFieldReferenceExpression CodeGotoStatement CodeIndexerExpression CodeIterationStatement CodeLabeledStatement CodeLinePragma CodeMemberEvent CodeMemberField CodeMemberMethod CodeMemberProperty CodeMethodInvokeExpression CodeMethodReferenceExpression CodeMethodReturnStatement CodeNamespace CodeNamespaceCollection CodeNamespaceImport CodeNamesapceImportCollection CodeObject CodeObjectCreateExpression

22. CodeDOM – even more CodeCompiler CodeDomProvider CodeGenerator CodeGeneratorOptions CodeParser CompilerError CompilerErrorCollection CompilerParameters CompilerResults Executor IndentedTextWriter TempFileCollection ICodeCompiler ICodeGenerator ICodeParser CodeBinaryOperatorType FieldDirection MemberAttributes CodePropertySetValueReferenceExpression CodeRemoveEventStatement CodeSnippetCompileUnit CodeSnippetExpression CodeTypeMemberCollection CodeTypeOfExpression CodeTypeReference CodeTypeReferenceCollection CodeTypeReferenceExpression CodeVariableDeclarationStatement CodeVariableReferenceExpression CodeCatchClause CodeCatchClauseCollection CodeComment CodeCommentStatement CodeCommentStatementCollection CodeCompileUnit CodeConditionStatement CodeConstructor CodeDelegateCreateExpression CodeDelegateInvokeExpression CodeDirectionExpression CodeEntryPointMethod CodeEventReferenceExpression CodeExpression CodeSnippetStatement CodeSnippetTypeMember CodeStatementCollection CodeThisReferenceExpression CodeThrowExceptionStatement CodeTryCatchFinallyStatement CodeTypeConstructor CodeTypeDeclaration CodeTypeDeclarationCollection CodeTypeDelegate CodeTypeMember

23. Dynamic Invocation with Brut force compilation Dynamic Invocation with Brut force CodeDOM Dynamic Invocation with CodeDOM

24. CodeDOM – Bottom line A lot of goodies, but very complicated yet limited … also you can write your own CodeDomProvider … however, if you can generate the CodeDom, it does not mean you can generate code with it

26. IL introduction IL – The language for execution Independent of CPU and platform Created by Microsoft, external commercial and academic language/compiler writers Stack based virtual machine: 5 + 10 - 3 IL_0001: ldc.i4 5 IL_0002: ldc.i4 10 IL_0003: add IL_0004: ldc.i4 3 IL_0005: sub Evaluation Stack 0000 005 0000 0010 0000 0015 0000 0003 0000 0012

27. IL introduction IL storage opcodes Locals of a method Fields in a class string str = “Hello, World!” IL_0001: ldstr “Hello, World!” IL_0002: stloc str IL_0003: ldloc str Foo.f = “Hello, World!” IL_0001: ldstr “Hello, World!” IL_0002: stfld string Foo::f IL_0003: ldfld string Foo::f

28. IL introduction IL control flow opcodes if (b) { ... } else { ... } IL_0001: ldloc b IL_0002: ldc.i4.1 IL_0003: ceq IL_0004: brfalse IL_00020 // if true statements IL_0010: ... IL_0011: br IL_00025 // else statements IL_0020: ... // rest of method IL_0025: ...

29. Reflection.Emit Assemblybuilder ConstructorBuilder CustomAttributeBuilder EnumBuilder EventBuilder FieldBuilder ILGenerator Label LocalBuilder MethodBuilder ModuleBuilder ParameterBuilder PropertyBuilder TypeBuilder

30. Code Emitting public class MyClass { public static void Main() { string str = “Hello World!”; Console.WriteLine (str); } } AssemblyBuilder ModuleBuilder TypeBuilder MethodBuilder LocalBuilder ILGenerator OPCodes

31. Lightweight Code Generation DynamicMethod Kid CloneKid(Kid) { newKid.Height = oldKid.Height newKid.Weight = oldKid.Weight } DynamicMethod ILGenerator OPCodes

32. Dynamic Invocation with Emit

34. HackMe All types in the CLR are self-describing DynamicMethod dm =… dm.GetMethodBody(). GetILAsByteArray (); MethodInfo mi = .. mi.GetMethodBody(). GetILAsByteArray ();

35. What's new in .NET 3.5? Lambdas .Compile() for code generation Expression Trees Parse and understand

36. From delegate to Lambda Delegate void SomeDelegate(EventsArgs e); Object.SomeEvent += new SomeDelegate(SomeMethod); Delegate Object.SomeEvent += delegate(EventArgs e) { //work here } Anonymous delegate Object.SomeEvent += (e) => { //work here }; Lambda

37. Expression Tree Use Expression<T> Parse Lambdas at runtime Compile at runtime (Expression.Compile()) Use the Expression Tree Debug Visualizer http://code.msdn.microsoft.com/csharpsamples

38. Parse and visualize trees Compile Lambdas

39. Related Content Today 14:45 – Team Foundation Server – Brian Randell – Session room 06 16:45 – Data Protection with CryptoAPI – Rafael Lukawiecki – Session room 06 or Optimizing your WPF application by me – Session room 09 19:30 – BEACH PARTY! Tomorrow 9:00 – Best Practicies for the VB.NET and C# – Lisa Feigenbaum – Session room 07 10:15 – Making your test lab obsolete – Brian Randell – Session room 07

40. Resources www.microsoft.com/teched Tech·Talks Tech·Ed Bloggers Live Simulcasts Virtual Labs http://microsoft.com/technet Evaluation licenses, pre-released products, and MORE! http://microsoft.com/msdn Developer’s Kit, Licenses, and MORE!

41. Please complete an evaluation

43. © 2008 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries. The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.