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Understanding Reflection

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  • 06/07/09 17:53 © 2007 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.
  • Transcript

    • 1.  
    • 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 }
    • 19.  
    • 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
    • 25.  
    • 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
    • 33.  
    • 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
    • 42.  
    • 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.