C# Collections & LINQ.

The containers a C# program uses and the query operators that read them. Covers 12 topics.

• C# Collections & LINQ · 1 of 3

  Dictionaries & sets

  In C#, what does HashSet<T> store?

  AElements with every duplicate keptBKey-value pairs with unique keysCDistinct elements, no duplicatesDElements kept in sorted order

• C# Collections & LINQ · 2 of 3

  LINQ performance

  In C#, what does a deferred LINQ query repeat each time it is enumerated?

  ANothing after the first runBOnly the final operatorCOnly the source readingDEvery step of the pipeline

• C# Collections & LINQ · 3 of 3

  Deferred execution

  In C#, the same Where query's Count() gives two different numbers within one request. Based on this program, what explains it?

  using System.Linq;var nums = new List<int> { 1, 2 };var q = nums.Where(n => n > 0);Console.WriteLine(q.Count());nums.Add(3);Console.WriteLine(q.Count());

  AWhere rebuilt the query on AddBCount() caches only the first result it gotCthe list changed between enumerationsDthe lambda ran twice for each item