Level Up Your Functional Programming Skills with LINQ
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In this presentation, Cameron Presley shows you how to implement basic LINQ Operations leveraging Funcs, Generics, and Extension Methods. Once fundamentals are in place, Cameron starts building the various LINQ methods
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Level Up Your Functional Programming Skills with LINQ
- 1. @pcameronpresley Level Up on FP Rebuilding LINQ Cameron Presley Cameron@TheSoftwareMentor.com
- 3. @pcameronpresley What is LINQ? Fundamentals Implementing the Trinity 3
- 4. 4
- 6. @pcameronpresley 6 Which Delivery Teams Have More Than 7 Members?
- 9. @pcameronpresley “Set of operations that works on data independent of the source In addition, these operations are type safe, allowing the compiler to catch your mistakes sooner 9
- 11. @pcameronpresley What Makes LINQ Work? 1. Func 2. Generics 3. Extension Methods 11
- 12. @pcameronpresley Getting Functional with Funcs! 12
- 13. @pcameronpresley Background ◦ Introduced in C# 3.0 ◦ Type that when invoked returns a value ◦ Requires 0 or more parameters 13
- 14. @pcameronpresley
- 19. @pcameronpresley Background ◦ Introduced in C# 2.0 ◦ Allows for type parameters for various constructs ◦ Great for when the type doesn’t matter for implementation 19
- 21. @pcameronpresley
- 23. @pcameronpresley When Generics Make Sense When you’re writing the third structure in a row… Logic is the same, only the types are different 23
- 24. @pcameronpresley 24 Extending Type Functionality Extension Methods
- 25. @pcameronpresley Background ◦ Introduced in C# 3.0 ◦ Extends functionality to types without having to recompile or creating a new type ◦ Great for when working with types you don’t have access to 25
- 27. @pcameronpresley 27 You Could Have Invented LINQ!
- 28. @pcameronpresley “The most common extension methods are the LINQ standard query operators that add query functionality to the existing System.Collections.IEnumerable and System.Collections.Generic.IEnumerable <T> types. 28 MS Docs on Extension Methods
- 29. 29
- 30. @pcameronpresley Design Guidelines ◦ Extend the IEnumerable type ◦ Same signatures of LINQ ◦ Same properties as LINQ 30
- 31. @pcameronpresley Changing Types with Map 31
- 32. @pcameronpresley Background Changes a collection of one type to another by using a mapper function Maintains the length of the collection 32
- 33. @pcameronpresley 33 Given a collection of DeliveryTeams, we want to see the names, so we write the following
- 35. @pcameronpresley 35 Given a collection of DeliveryTeams, we want to see the TeamLeads, so we write the following
- 38. @pcameronpresley
- 39. @pcameronpresley 39 Given a collection of DeliveryTeams, we want to know the number of team members on each team
- 43. @pcameronpresley 43 Any reason we need to constraint this to the DeliveryTeam type?
- 44. @pcameronpresley 44 Select Imp from GitHub
- 45. @pcameronpresley 45 Do we need to limit to List<TSource> and List<TResult>?
- 46. @pcameronpresley “Use Map to Transform the Collection Into The Data You Need 46
- 47. @pcameronpresley Keeping What’s Needed with Keep 47
- 48. @pcameronpresley Background Returns a subset of a collection based on a predicate Length is between 0 and original length Doesn’t return items that weren’t in the list Maintains order 48
- 49. 49 Which DeliveryTeams have more than 7 team members?
- 50. 50 Which DeliveryTeams have Dana as a TeamLead?
- 51. 51
- 52. 52
- 54. @pcameronpresley 54 Any reason why this would be limited to DeliveryTeam?
- 55. 55
- 56. @pcameronpresley 56 Where Implementation from GitHub
- 57. @pcameronpresley “Use Keep to Keep Data That You Want 57
- 58. @pcameronpresley Going from many to one with Reduce 58
- 59. @pcameronpresley Background Takes a collection, an initial value, and a combiner method, returns a single value 59
- 60. @pcameronpresley 60 How many team members do we have in total?
- 65. @pcameronpresley 65 Any reason why this should only work on DeliveryTeam?
- 67. @pcameronpresley 67 Aggregate Imp from GitHub
- 68. @pcameronpresley “Use Reduce to Transform a Collection to a Single Value by First Identifying the Initial Value, Followed by Writing the Combining Logic 68
- 69. @pcameronpresley Reducing LINQ to Reduce 69 No, Seriously…
- 70. @pcameronpresley Breaking Down The Problem ◦ Determine the Initial Value ◦ Determine how to combine the initial value with the next element 70
- 71. @pcameronpresley 71 What’s the initial value? What should we return if the source is empty? Enumerable<TResult>.Empty()
- 72. @pcameronpresley Setting Up Map via Reduce 72 1. Covert item from T to TResult 2. Append the converted item to values
- 73. @pcameronpresley Converting from T to TResult 73
- 75. @pcameronpresley Redoing Keep as Reduce 75
- 76. @pcameronpresley 76 What’s the initial value? What should we return if the source is empty? Enumerable<TSource>.Empty()
- 77. @pcameronpresley Setting Up Keep via Reduce 77 1. Check if the item meets the criteria 2. If the item meets, append to values %%
- 78. @pcameronpresley Checking if an item is valid 78
- 80. @pcameronpresley What Did We Cover? What is LINQ? Fundamentals (Func, Generics, Extension Methods) Implementing Map, Keep, Reduce 80
- 82. @pcameronpresley Composition of Funcs, Generics, Extension Methods 82
- 83. @pcameronpresley Building bigger programs from smaller programs 83