All about Attributes, Reflection, and Dynamic Programming

1. Attributes, Reflection, and
Dynamic Programming
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2. Decorating Code With

3. Decorating Code With
• Demo

4. Examples of
Applications That Use
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5. Examples of
Applications That Use
• Attributes are meta-data you can add
to code
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6. Examples of
Applications That Use
• Attributes are meta-data you can add
to code
• Examples of applications:
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7. Examples of
Applications That Use
• Attributes are meta-data you can add
to code
• Examples of applications:
• The C# compiler
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8. Examples of
Applications That Use
• Attributes are meta-data you can add
to code
• Examples of applications:
• The C# compiler
• Web Services
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9. Examples of
Applications That Use
• Attributes are meta-data you can add
to code
• Examples of applications:
• The C# compiler
• Web Services
• Unit testing
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10. C# Compiler Attribute

11. C# Compiler Attribute
• ObsoleteAttribute marks code as being
deprecated

12. C# Compiler Attribute
• ObsoleteAttribute marks code as being
deprecated
• ConditionalAttribute removes code
when a pre-processing directive isn’t
defined

13. C# Compiler Attribute
• ObsoleteAttribute marks code as being
deprecated
• ConditionalAttribute removes code
when a pre-processing directive isn’t
defined
• DllImportAttribute enables calling
Windows OS APIs

14. Creating New Attributes

15. Creating New Attributes
• Demo

16. Deriving From Attribute

17. Deriving From Attribute
• Derive a new class from Attribute,
a .NET Framework type

18. Deriving From Attribute
• Derive a new class from Attribute,
a .NET Framework type
• Give your class a suffix of “Attribute”

19. Deriving From Attribute
• Derive a new class from Attribute,
a .NET Framework type
• Give your class a suffix of “Attribute”
• i.e. TestAttribute

20. Deriving From Attribute
• Derive a new class from Attribute,
a .NET Framework type
• Give your class a suffix of “Attribute”
• i.e. TestAttribute
• Not required, but a common convention

21. Specifying Named and Positional
Parameters

22. Specifying Named and Positional
Parameters
• Positional parameters appear first

23. Specifying Named and Positional
Parameters
• Positional parameters appear first
• Named parameters follow

24. Specifying Named and Positional
Parameters
• Positional parameters appear first
• Named parameters follow
• For:

25. Specifying Named and Positional
Parameters
• Positional parameters appear first
• Named parameters follow
• For:
[DllImport("shell32.dll", EntryPoint="FindExecutable")]

26. Specifying Named and Positional
Parameters
• Positional parameters appear first
• Named parameters follow
• For:
[DllImport("shell32.dll", EntryPoint="FindExecutable")]
• “shell32.dll” is positional

27. Specifying Named and Positional
Parameters
• Positional parameters appear first
• Named parameters follow
• For:
[DllImport("shell32.dll", EntryPoint="FindExecutable")]
• “shell32.dll” is positional
• EntryPoint="FindExecutable" is named

28. Decorating with
AttributeUsageAttribute

29. Decorating with
AttributeUsageAttribute
• Three Parameters

30. Decorating with
AttributeUsageAttribute
• Three Parameters
• AllowMultiple – can use attribute more
than once

31. Decorating with
AttributeUsageAttribute
• Three Parameters
• AllowMultiple – can use attribute more
than once
• Inherited – applies to derived classes

32. Decorating with
AttributeUsageAttribute
• Three Parameters
• AllowMultiple – can use attribute more
than once
• Inherited – applies to derived classes
• ValidOn – defines where allowed to use

33. Using Reflection

34. Using Reflection
• Demo

35. Getting Type and TypeInfo

36. Getting Type and TypeInfo
• Reflection API split into two types

37. Getting Type and TypeInfo
• Reflection API split into two types
• Type provides reference support

38. Getting Type and TypeInfo
• Reflection API split into two types
• Type provides reference support
• TypeInfo offers execution support

39. Exploring Type Members

40. Exploring Type Members
• Once you have a type, you can query
its members:

41. Exploring Type Members
• Once you have a type, you can query
its members:
• GetFields

42. Exploring Type Members
• Once you have a type, you can query
its members:
• GetFields
• GetMethods

43. Exploring Type Members
• Once you have a type, you can query
its members:
• GetFields
• GetMethods
• GetProperties

44. Exploring Type Members
• Once you have a type, you can query
its members:
• GetFields
• GetMethods
• GetProperties
• GetXxx

45. Exploring Type Members
• Once you have a type, you can query
its members:
• GetFields
• GetMethods
• GetProperties
• GetXxx
• Continue to explore as you need

46. Dynamic Invocation

47. Dynamic Invocation
• You can dynamically invoke/run
methods discovered through reflection

48. Dynamic Invocation
• You can dynamically invoke/run
methods discovered through reflection
• Get object reference, if instance

49. Dynamic Invocation
• You can dynamically invoke/run
methods discovered through reflection
• Get object reference, if instance
• Specify parameters

50. Dynamic Invocation
• You can dynamically invoke/run
methods discovered through reflection
• Get object reference, if instance
• Specify parameters
• Call Invoke(…)

51. Dynamic Invocation
• You can dynamically invoke/run
methods discovered through reflection
• Get object reference, if instance
• Specify parameters
• Call Invoke(…)
• Code runs

52. Coding Dynamic Types

53. Coding Dynamic Types
• Demo

54. Using Dynamic Types

55. Using Dynamic Types
• Declare type as dynamic

56. Using Dynamic Types
• Declare type as dynamic
• Can call any member

57. Using Dynamic Types
• Declare type as dynamic
• Can call any member
• Can assign to any member

58. Using Dynamic Types
• Declare type as dynamic
• Can call any member
• Can assign to any member
• No compile-time error

59. Using Dynamic Types
• Declare type as dynamic
• Can call any member
• Can assign to any member
• No compile-time error
• Errors surface as runtime exceptions

60. The Expando Object

61. The Expando Object
• Lets you add/remove members
dynamically

62. The Expando Object
• Lets you add/remove members
dynamically
• Can pass object reference as
parameter

63. The Expando Object
• Lets you add/remove members
dynamically
• Can pass object reference as
parameter
• Use members dynamically too

64. The Expando Object
• Lets you add/remove members
dynamically
• Can pass object reference as
parameter
• Use members dynamically too
• Get notified when add/remove occurs

65. Implementing

66. Implementing
• Derive from DynamicObject

67. Implementing
• Derive from DynamicObject
• Overrides let you do anything
dynamically

68. Implementing
• Derive from DynamicObject
• Overrides let you do anything
dynamically
• Examples of methods you can override

69. Implementing
• Derive from DynamicObject
• Overrides let you do anything
dynamically
• Examples of methods you can override
• TrySetMember

70. Implementing
• Derive from DynamicObject
• Overrides let you do anything
dynamically
• Examples of methods you can override
• TrySetMember
• TryGetMember

71. Implementing
• Derive from DynamicObject
• Overrides let you do anything
dynamically
• Examples of methods you can override
• TrySetMember
• TryGetMember
• TryInvokeMember

72. Questions?
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73. Questions?
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