Deep Reflection

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Deep Reflection
noitcelfeR peeD
Cool Hot Reflection 2.03.5 Features
Roy Osherove, Typemock www.ISerializable.com
(blog)
Roy_at_Osherove.com
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Assumption You already know Reflection
3
Agenda

• Generate Code
• Reflection.Emit in 3 Minutes
• Easier
• Faster Code
• Debuggable
• Visualizable
• Inspect Code at Runtime
• More Securely
• Inspect methods IL
• 3.5
• Lambdas and compile
• Expression Trees

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Generating Code

• Why?

5
The Cloning/Serializing Problem

• Person
• Name
• Age
• Order
• GUID
• Customer
• Handle any Object Quickly

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The Cloning/Serializing ProblemClassic Reflection
UnknownObject
Gettype().GetMembers()
For Each Member FieldInfo.Copy old value to new
Object
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The Cloning/Serializing ProblemOptimized
UnknownObject
Gettype().GetMemebers()
For Each Member Create Code That Copies
member newObj.Name oldObj.Name
Person ClonePerson(Person) newPerson.Name
old.Name Newperson.Age old.Age
Save as Method for later Invocation
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The Cloning/Serializing ProblemAfter Optimization
UnknownObject
HasCustomMethod?
Person ClonePerson(Person) newPerson.Name
old.Name Newperson.Age old.Age
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Generating Code
Person ClonePerson(Person) newPerson.Name
old.Name Newperson.Age old.Age

• CodeDom
• Reflection.Emit

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CodeDOM
CodeEntryPointMethod start new
CodeEntryPointMethod() CodeMethodInvokeExpressi
on cs1 new CodeMethodInvokeExpression( new
CodeTypeReferenceExpression("System.Console"),
"WriteLine", new CodePrimitiveExpression("Hello
World!") ) start.Statements.Add(cs1)
Public static void Main() System.Console.WriteL
ine(Hello World!)
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CodeDOM

• CodeArgumentReferenceExpression
• CodeArrayCreateExpression
• CodeArrayIndexerExpression
• CodeAssignStatement
• CodeAttachEventStatement
• CodeAttributeArgument
• CodeAttributeArgumentCollection
• CodeAttributeDeclaration
• CodeAttributeDeclarationCollection
• CodeBaseReferenceExpression
• CodeBinaryOperatorExpression
• CodeCastExpression
• CodeCatchClause
• CodeCatchClauseCollection
• CodeComment
• CodeCommentStatement
• CodeCommentStatementCollection
• CodeCompileUnit
• CodeConditionStatement

• CodeExpressionCollection
• CodeExpressionStatement
• CodeFieldReferenceExpression
• CodeGotoStatement
• CodeIndexerExpression
• CodeIterationStatement
• CodeLabeledStatement
• CodeLinePragma
• CodeMemberEvent
• CodeMemberField
• CodeMemberMethod
• CodeMemberProperty
• CodeMethodInvokeExpression
• CodeMethodReferenceExpression
• CodeMethodReturnStatement
• CodeNamespace
• CodeNamespaceCollection
• CodeNamespaceImport
• CodeNamesapceImportCollection

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More

• CodeCompiler
• CodeDomProvider
• CodeGenerator
• CodeGeneratorOptions
• CodeParser
• CompilerError
• CompilerErrorCollection
• CompilerParameters
• CompilerResults
• Executor
• IndentedTextWriter
• TempFileCollection
• ICodeCompiler
• ICodeGenerator
• ICodeParser
• CodeBinaryOperatorType
• FieldDirection

• CodePropertySetValueReferenceExpression
• CodeRemoveEventStatement
• CodeSnippetCompileUnit
• CodeSnippetExpression
• CodeTypeMemberCollection
• CodeTypeOfExpression
• CodeTypeReference
• CodeTypeReferenceCollection
• CodeTypeReferenceExpression
• CodeVariableDeclarationStatement
• CodeVariableReferenceExpression

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Even More

• CodeEventReferenceExpression
• CodeExpression
• CodeSnippetStatement
• CodeSnippetTypeMember
• CodeStatementCollection
• CodeThisReferenceExpression
• CodeThrowExceptionStatement
• CodeTryCatchFinallyStatement
• CodeTypeConstructor
• CodeTypeDeclaration
• CodeTypeDeclarationCollection
• CodeTypeDelegate
• CodeTypeMember

• CodeCatchClause
• CodeCatchClauseCollection
• CodeComment
• CodeCommentStatement
• CodeCommentStatementCollection
• CodeCompileUnit
• CodeConditionStatement
• CodeConstructor
• CodeDelegateCreateExpression
• CodeDelegateInvokeExpression
• CodeDirectionExpression
• CodeEntryPointMethod

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Generating Code With CodeDOM
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Generating Code With CodeDOM
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(No Transcript)
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The full picture
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CodeDom Half Baked

• Creation of Param Arrays
• Creation of Finalizers
• Static Events
• Readonly fields
• Cant Control String Literals (_at_string)
• Cant Control Order of Implementation
• Partial methods
• Auto properties
• Auto initializers, var, lambdas.

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Agenda

• From CodeDom to Reflection.Emit

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Reflection.Emit
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IL in 3 Minutes
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CLR Internals

• IL The language for execution
• Independent of CPU and platform
• Created by Microsoft, external commercial and
  academic language/compiler writers
• Stack based virtual machine

10 20 - 5 IL_0001 ldc.i4 10
IL_0002 ldc.i4 20 IL_0003 add
IL_0004 ldc.i4.5 IL_0005 sub
Evaluation Stack
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CLR Internals

• IL The language for execution
• Independent of CPU and platform
• Created by Microsoft, external commercial and
  academic language/compiler writers
• Stack based virtual machine

10 20 - 5 IL_0001 ldc.i4 10
IL_0002 ldc.i4 20 IL_0003 add
IL_0004 ldc.i4.5 IL_0005 sub
0000 0010
Evaluation Stack
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CLR Internals

• IL The language for execution
• Independent of CPU and platform
• Created by Microsoft, external commercial and
  academic language/compiler writers
• Stack based virtual machine

10 20 - 5 IL_0001 ldc.i4 10
IL_0002 ldc.i4 20 IL_0003 add
IL_0004 ldc.i4.5 IL_0005 sub
0000 0020
0000 0010
Evaluation Stack
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CLR Internals

• IL The language for execution
• Independent of CPU and platform
• Created by Microsoft, external commercial and
  academic language/compiler writers
• Stack based virtual machine

10 20 - 5 IL_0001 ldc.i4 10
IL_0002 ldc.i4 20 IL_0003 add
IL_0004 ldc.i4.5 IL_0005 sub
0000 0030
Evaluation Stack
26
CLR Internals

• IL The language for execution
• Independent of CPU and platform
• Created by Microsoft, external commercial and
  academic language/compiler writers
• Stack based virtual machine

10 20 - 5 IL_0001 ldc.i4 10
IL_0002 ldc.i4 20 IL_0003 add
IL_0004 ldc.i4.5 IL_0005 sub
0000 0005
0000 0030
Evaluation Stack
27
CLR Internals

• IL The language for execution
• Independent of CPU and platform
• Created by Microsoft, external commercial and
  academic language/compiler writers
• Stack based virtual machine

10 20 - 5 IL_0001 ldc.i4 10
IL_0002 ldc.i4 20 IL_0003 add
IL_0004 ldc.i4.5 IL_0005 sub
0000 0025
Evaluation Stack
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CLR Internals

• IL storage opcodes
• Locals of a method
• Fields in a class

string a hello world IL_0001 ldstr
hello world IL_0002 stloc a
IL_0003 ldloc a
foo.f hello world IL_0001 ldstr
hello world IL_0002 stfld string
Foof IL_0003 ldfld string Foof
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CLR Internals

• IL control flow opcodes

if (a) ... else ... IL_0001
ldloc a 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 ...
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CLR Internals

• System.Reflection.Emit namespace used to generate
  code
• Builder APIs derive from Reflection

Reflection.Emit APIs needed
C source
public class FooClass public static void
Main () string x hello world!
Console.WriteLine(x)
AssemblyBuilder
ModuleBuilder
TypeBuilder
MethodBuilder
ILGenerator
OpCodes
LocalBuilder
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Classic Reflection.Emit

• Demo

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Its Easier
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Lightweight Code Gen (LCG)

• DynamicMethod

Reflection.Emit APIs needed
C source
public static void MyMethod () string x
hello world! Console.WriteLine(x)
DynamicMethod
ILGenerator
OpCodes
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DynamicMethod

• Demo

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Cloning Optimization Skip Visibility Checks
Cloner
PersonBase

• Demo

PersonWithAge
PersonWithMoreProperties
PersonWithNumber
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Perf Gains with Reflection.Emit
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Reflection.Emit DynamicMethod

• Creates full Assembly, Module and Type
• Stays in memory until AppDomain dies
• Verify correctness PEVerify.exe,
• IL Debugger
• IDE Debugger
• Visualizer

• Create single static method on existing type
• Garbage Collected
• Verify correctness Visualizer
• Can skip visibility checks

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Run-Sharp

• Demo

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Finding Problems in IL

• Visualizers

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LCG Visualizer Demo
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Its Debuggable
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Debugging Generated Code

• Symbol Support
• Set Debuggable(DisableOptimizations) on
  Assembly
• ISymbolDocumentWriter ?(Module.DefineDocument)
• Gen.MarkSequencePoint(2,1,2,100)
• Local.SetLocalSymInfo

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Debugging Generated Code

• Demo

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Its More Secure
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Reflection Hackers
MyApp

• Demo
• Reflecting for Plugins

MyPlugins
PluginSDK
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Reflection-Only Context

• Reflect on Type and Assembly for Meta-Data
• Late-Bound Invocation
• Loader Concept
• Special APIs Added
• Invocations are disabled

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Reflection-Only Context

• Assembly asm Assembly.ReflectionOnlyLoad("asm.dl
  l")
• Type t Type.ReflectionOnlyGetType("MyType",
  false, false)
• GetRawXXX()
• GetCustomAttributes ? No more
• CustomAttributeData

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ReflectionOnly Demo

• Safer Loading

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Reflection over MethodBody

• DynamicMethod dm
• Dm.GetMethodBody().GetILAsByteArray())
• MethodInfo mi ..
• Mi.GetMethodBody().GetILAsByteArray()

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Reflection in .NET 3.5

• Lambdas
• .Compile() for code generation
• Expression Trees
• Parse and understand

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Why should I care?

• Concise Syntax Saves typing
• Can generate code
• Can be parsed
• Mathematical Lambda Calculus
• Functional Languages (Python,F..)
• Functions Objects, with statements
• Executable, but also brows-able

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From delegate to Lambda

• Delegate void SomeDelegate(EventsArgs e)
• Object.SomeEvent new SomeDelegate(Amethod)
• String s
• Object.SomeEvent delegate(EventArgs e)
• //work here
• Lambda
• Object.SomeEvent (e) gt //work here
• Shorter
• No need to put parameter types
• can be parsed into an Expression Tree

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Expression Trees

• Use ExpressionltTgt
• Parse Lambdas at runtime
• Compile at runtime (Expression.Compile())
• Use the Expression Tree Debug Visualizer
• VS 2008-Help-Samples-Samples on disk-local
  samples folder-
• csharpSamples-LinqSamples-ExpressionTreeVisualizer
  

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Demo Parse and Visualize Trees
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Demo Compile Lambda
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Pre-Song Summary

• Reflection can be overused
• Use Secure reflection
• Optimize when needed - use Code Gen
• Use the visualizers to debug it
• If generating long code add debug symbols
• Powerful art IF you know what youre doing

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Pre-Song Resources

• Joel Pobars Weblog
• http//blogs.msdn.com/joelpob/
• MethodBase Visualizer
• http//tinyurl.com/nac58
• Mdbg
• http//tinyurl.com/3ksg2
• TestDriven.NET
• www.testdriven.net (Debugging and Testing Addin)
• Roys Weblog
• Roy_at_Osherove.com
• ISerializable.com

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I dont want to blog about it

• This is a test line

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• It looks like youre doing just fine

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• Its time for a song of mine!

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I dont want to blog about it

• I can tell by your eyes that youve probably
• been coding forever
• And your codes so complex
• That the chance of us fixing it is - never

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• I dont wanna blog about it
• How you made this mess
• I wish you never learned reflection,
• Baby
• I wish reflection in our code
• Was much less.
• Oh yes..

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• I can tell by your code that were
• Going to debug it
• Forever
• There are no unit tests
• Oh man, you must think youre so clever

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• Now its time to
• Talk about it
• Man your code just sucks
• Now your work is full of unreadable Reflection
• You need guidance and direction
• Oh so much

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• Thank you!
• Roy_at_Osherove.com