This chapter introduced LINQ (Language Integrated Query), a powerful feature for querying data. We showed how to filter an array or collection using LINQ’s where clause, and how to sort the query results using the orderby clause. We used the select clause to select specific properties of an object, and the let clause to introduce a new range variable to make writing queries more convenient. The StartsWith method of class string was used to filter strings starting with a specified character or series of characters. We used several LINQ extension methods to perform operations not provided by the query syntax—the Distinct method to remove duplicates from the results, the Any method to determine if the results contain any items, and the First method to retrieve the first element in the results.

We introduced the List<T> generic collection, which provides all the functionality of arrays, along with other useful capabilities such as dynamic resizing. We used method Add to append new items to the end of the List, method Insert to insert new items into specified locations in the List, method Remove to remove the first occurrence of a specified item, method RemoveAt to remove an item at a specified index and method Contains to determine if an item was in the List. We used property Count to get the number of items in the List, and property Capacity to determine the number of elements the List can hold without growing. We use more advanced features of LINQ in later chapters.

In Chapter 10 we take a deeper look at class concepts. We’ll discuss the this reference, additional constructor concepts, how the runtime manages memory with garbage collection, static class members, read-only class members, object initializers and operator overloading.