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

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

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

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

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)

“ 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)

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

System.Reflection namespace contains most Reflection classes.

System.Type is Reflection class used to access type metadata.

… more…

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

Viewing metadata

Performing type discovery

Late binding to methods and properties (Dynamic Invocation)

Creating types at runtime (Reflection Emit)

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. …

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.

…

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

Value, Interface or Class?

IsValueType, IsInterface, IsClass

Public, Private or Sealed ?

IsNotPublic, IsSealed

Abstract or Implementation?

IsAbstract

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

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

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

Base class for all "member" element descriptions

Fields, Properties, Methods, etc.

Provides member kind, name and declaring class

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

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

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

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

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

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

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

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

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

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 }

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

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!”); }

CodeEntryPointMethod start = new CodeEntryPointMethod();

CodeMethodInvokeExpression cs1 =

new CodeMethodInvokeExpression(

new CodeTypeReferenceExpression ("System.Console"),

"WriteLine",

new CodePrimitiveExpression ("Hello World!") );

start.Statements.Add(cs1);

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

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

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

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

Dynamic Invocation with Brut force compilation Dynamic Invocation with Brut force CodeDOM Dynamic Invocation with CodeDOM

Dynamic Invocation with Brut force compilation

Dynamic Invocation with Brut force CodeDOM

Dynamic Invocation with CodeDOM

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

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

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

IL – The language for execution

Independent of CPU and platform

Created by Microsoft, external commercial and academic language/compiler writers

Stack based virtual machine:

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

IL storage opcodes

Locals of a method

Fields in a class

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: ...

IL control flow opcodes

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

Assemblybuilder

ConstructorBuilder

CustomAttributeBuilder

EnumBuilder

EventBuilder

FieldBuilder

ILGenerator

Label

LocalBuilder

MethodBuilder

ModuleBuilder

ParameterBuilder

PropertyBuilder

TypeBuilder

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

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

DynamicMethod

Dynamic Invocation with Emit

Dynamic Invocation with Emit

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

All types in the CLR are self-describing

DynamicMethod dm =…

dm.GetMethodBody(). GetILAsByteArray ();

MethodInfo mi = ..

mi.GetMethodBody(). GetILAsByteArray ();

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

Lambdas

.Compile() for code generation

Expression Trees

Parse and understand

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

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

Use Expression<T>

Parse Lambdas at runtime

Compile at runtime (Expression.Compile())

Use the Expression Tree Debug Visualizer

http://code.msdn.microsoft.com/csharpsamples

Parse and visualize trees Compile Lambdas

Parse and visualize trees

Compile Lambdas

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

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

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