Ch10.md

Chapter 10 Examples

Examples from Chapter 10 (LINQ) of Programming C# 10.0 (O'Reilly).

Query Expressions

• Example 1. A LINQ query expression
• Example 2. The non-LINQ equivalent
• Example 3. Extracting just one property in a query
• Example 4. The effect of a query expression
• Example 5. How trivial select clauses expand
• Example 6. Query with a let clause
• Example 7. How multivariable query expressions expand (approximately)
• Example 8. Nonsensical Where and Select
• Example 9. A meaningless query
• Example 10. How the compiler transforms the meaningless query
• Example 11. A custom LINQ provider for CultureInfo[]

Deferred Evaluation

• Example 12. Query with an infinite source sequence
• Example 13. A custom deferred Where operator
• Example 14. Accidental reevaluation of a deferred query

LINQ, Generics, and IQueryable<T>

• Example 15. IQueryable and IQueryable<T>
• Example 16. Enumerable versus Queryable

Standard LINQ Operators

• Example 17. Sample input data for LINQ queries

Filtering

• Example 18. Where operator with index
• Example 19. The OfType<T> operator

Select

• Example 20. Select operator with index
• Example 21. Indexed Select downstream of Where operator
• Example 22. Indexed Select upstream of Where operator
• Example 23. Fetching more data than is needed
• Example 24. A select clause with an anonymous type
• Example 25. Using Select to transform numbers

SelectMany

• Example 26. Using SelectMany from a query expression
• Example 27. SelectMany operator
• Example 28. Flattening a jagged array
• Example 29. SelectMany without item projection
• Example 30. One implementation of SelectMany

Chunkining

• Example 31. Splitting a sequence into batches with Chunk

Ordering

• Example 32. Query expression with orderby clause
• Example 33. How not to apply multiple ordering criteria
• Example 34. Multiple ordering criteria in a query expression
• Example 35. Multiple ordering criteria with LINQ operators

Specific Items and Subranges

• Example 36. Applying the Single operator to a query
• Example 37. Single operator with predicate
• Example 38. Using First to select the longest course
• Example 39. SingleOrDefault with explicit default value
• Example 40. How not to use ElementAt

Aggregation

• Example 41. Average operator with projection
• Example 42. Max with projection
• Example 43. Max with projection for criteria but not for result
• Example 44. Max with projection for criteria but not for result with error on empty input
• Example 45. Sum and equivalent with Aggregate
• Example 46. Implementing Max with Aggregate
• Example 47. Implementing Average with Aggregate
• Example 48. Aggregating bounding boxes
• Example 49. More verbose and less obscure bounding box aggregation
• Example 50. The effect of Aggregate

Set Operations

• Example 51. Removing duplicates with Distinct

Whole-Sequence, Order-Preserving Operations

• Example 52. Combining lists with Zip

Grouping

• Example 53. Grouping query expression
• Example 54. Expanding a simple grouping query
• Example 55. Group query with item projection
• Example 56. Expanding a group query with an item projection
• Example 57. Group query with group projection
• Example 58. Expanded group query with group projection
• Example 59. GroupBy with key and group projections
• Example 60. GroupBy operator with key, item, and group projections
• Example 61. Composite group key

Joins

• Example 62. Record type associating a student with a course
• Example 63. Query with join clause
• Example 64. Using the Join operator directly
• Example 65. A grouped join
• Example 66. GroupJoin operator

Conversion

• Example 67. How not to cast a sequence
• Example 68. How to cast a sequence
• Example 69. Creating a lookup