Day 03 LINQ Deep Dive

Day 03 - Deep Dive into LINQ

Projects:

Fun With LINQ	Deep Dive into the features of LINQ

The Idea behind LINQ

• We have created extension methods on enumerables that create new enumerables - thus creating operators
• We have passed delegates to the methods in order to allow them to be a lot more flexible
• We made them even more flexible by converting them to generic methods so that they can run on any type of enumerables
• We have examined the deferred nature of the operators

LINQ To Data Entities

• We have seen how to load CSV data files into an enumerable of data entities using LINQ
• We have used the basic operators Select, Where, OrderBy and Take to create some basic queries
• We saw how to use the query syntax with keywords such as from, select, orderby, where and how they map to the fluent api extension methods

Second Order Operators

• We have defined the term Second order enumerable as an enumerable of enumerables.
• We have seen various ways to convert a first order enumerable to a second order enumerable: GroupBy, ToLookup
• We talked about the IGrouping interface
  • Extends the IEnumerable interface
  • Adds a Key property
  • Is a result of grouping methods
• We talked about how to convert second order enumerables back to flat enumerables by using the SelectMany operator

Data Structure Operators

• We talked about the data structure generators in LINQ ToArray, ToList, ToHashSet
• We have seen how to create a Mapping using ToDictionary
• We have sen how to create a One-To-Many mapping using ToLookup and how to use the result

Aggragation Operators

• We have seen how to use the Aggregate operator as a general way to produce a scalar value out of an enumerable
• We have seen how to use the most basic variation of Aggregate to sum or find the max in a collection of items
• We have seen how to use a seed and an accumulator to carry value between items of a collection
• We have seen how to use the most explicit version of Aggregate to finally convert the accumulator to the output result