Smoke and Mirrors Reflection in C

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Smoke and Mirrors- Reflection in C
Wekoslav Stefanovski
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What is reflection
Definition - to look back to itself
Run Time Type Information
Discovering class information solely at run time
.net Reflection
Assembly Access based on metadata
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System.Type

• Base of all reflection classes and properties -
  primary way to access metadata
• Represents all kinds of types (class, interface,
  enumeration)
• GetType() is a Method of System.Object
• typeof() operator returns Type object
• A Type is unique per type
• Only one instance of Type per type per
  application domain

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MemberInfo class

• Provides access to member metadata.
• MemberType propery is useful to determine the
  tipe of a member
• Ancestor to all other XXXInfo classes
• Actually an ancestor to Type

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Other XXXInfo Classes

• PropertyInfo
• GetGetMethod GetSetMethod
• FieldInfo
• GetValue SetValue
• MethodInfo
• Invoke
• ConstructorInfo
• EventInfo

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Attributes

• An information which marks the elements of code.
• A class that derives from System.Attribute
• Multiple points of consumption compiler, CLR,
  debugger, user code
• Can use both positional and named parameters

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Using Custom Attributes

• Type.GetCustomAttributes
• Attribute.GetCustomAttribute
• Only way to get information about attributes
  applied to an object in user code

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System.Activator

• A generalized way for creating objects at runtime
• CreateInstance method generic and regular
• Other Uses

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Reflection and Generics

• Difference between regular types, generic types,
  and specialized types
• Type.IsGenericType
• Type.IsGenericTypeDefinition
• Type.MakeGenericType
• MethodInfo.IsGenericMethod
• MethodInfo.IsGenericMethodDefinition

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Reflection.Emit

• Creating, modifying and running of code in
  runtime
• Does not use C, uses MSIL
• Very complex, very powerfull

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Speed of Reflecting

• As expected, direct access is much faster than
  reflection
• Performance hit anywhere from 5 to 150 times
  slower
• Avoid using lots of reflection in tight loops
• We should weight if the usefulness in the
  scenario justifies the slowdown.

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References

• Generics Terminology in .NET Framework -
  http//blogs.msdn.com/parthopdas/archive/2005/10/2
  1/483463.aspx
• Hello World.Emit - http//blogs.msdn.com/joelpob/a
  rchive/2004/01/21/61411.aspx
• Programming C Attributes and Reflection -
  http//www.ondotnet.com/pub/a/dotnet/excerpt/prog_
  csharp_ch18/index.html?page1
• How Microsoft Uses Reflection -
  http//msdn2.microsoft.com/en-us/magazine/cc163960
  .aspx
• Real-world Reflection in .NET -
  http//www.devx.com/dotnet/Article/31578/1954
• Reflection - Dodge Common Performance Pitfalls
  http//msdn2.microsoft.com/en-us/magazine/cc163759
  .aspx
• .NET Reflection Dynamically Bind Your Data Layer
  -http//msdn.microsoft.com/msdnmag/issues/02/08/N
  ETReflection/default.aspx
• And many others

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Questions?