| 1 | What is LINQ and what is deferred execution? C# › LINQ | C# | LINQ | Beginner |
| 2 | What is LINQ, and what are the two main syntax styles you can use to write a LINQ query? C# › LINQ | C# | LINQ | Beginner |
| 3 | What is the difference between Where() and Select() in a LINQ query? C# › LINQ | C# | LINQ | Beginner |
| 4 | What is the difference between IEnumerable and IQueryable in LINQ? C# › LINQ | C# | LINQ | Intermediate |
| 5 | What is 'deferred execution' in LINQ, and how does it differ from calling .ToList() or .ToArray() immediately? C# › LINQ | C# | LINQ | Intermediate |
| 6 | What is LINQ, and how does it simplify querying collections compared to writing manual loops? C# › LINQ | C# | LINQ | Intermediate |
| 7 | Why can LINQ cause the N+1 query problem and how do you fix it? C# › LINQ | C# | LINQ | Advanced |
| 8 | How does LINQ to Objects differ fundamentally from LINQ to Entities (Entity Framework), particularly regarding how the query is actually executed? C# › LINQ | C# | LINQ | Advanced |
| 9 | How would you write a custom LINQ extension method that integrates seamlessly with the standard method-chaining style, like a 'DistinctBy' before it existed natively? C# › LINQ | C# | LINQ | Advanced |
| 10 | How does LINQ's Aggregate() method work, and how would you use it to implement a custom reduction not covered by Sum()/Average()/Count()? C# › LINQ | C# | LINQ | Advanced |
| 11 | How would you write an efficient LINQ query combining Join() with GroupBy() to replicate a SQL-style LEFT OUTER JOIN with aggregation? C# › LINQ | C# | LINQ | Advanced |
| 12 | How would you optimize a LINQ-to-Entities query to avoid the classic 'N+1 query' performance problem when accessing related navigation properties? C# › LINQ | C# | LINQ | Advanced |
| 13 | How would you implement a custom lazy 'Where' and 'Select' from scratch using yield return, mirroring how LINQ actually works internally? C# › Iterators & yield return | C# | Iterators & yield return | Advanced |
| 14 | How do you configure and use raw SQL queries alongside LINQ in EF Core when a complex query is difficult or inefficient to express in LINQ? .NET › Entity Framework Core & Data Access | .NET | Entity Framework Core & Data Access | Intermediate |
| 15 | How does the 'yield return'-based lazy evaluation of collections (like LINQ or a custom iterator) differ from eagerly materializing a full collection, in terms of memory usage? C# › Collections | C# | Collections | Advanced |
| 16 | What is the difference between First, FirstOrDefault and Single? C# › LINQ | C# | LINQ | Intermediate |
| 17 | What is the difference between Select and SelectMany? C# › LINQ | C# | LINQ | Intermediate |
| 18 | How do GroupBy() and its resulting IGrouping<TKey, TElement> work? C# › LINQ | C# | LINQ | Intermediate |
| 19 | What is the difference between First(), FirstOrDefault(), Single(), and SingleOrDefault()? C# › LINQ | C# | LINQ | Intermediate |
| 20 | What is the difference between IEnumerable<T>, IQueryable<T>, and List<T>, and how does choosing the wrong one hurt performance against a database? C# › LINQ | C# | LINQ | Intermediate |
| 21 | How does GroupBy translate and what performance pitfalls exist? C# › LINQ | C# | LINQ | Advanced |
| 22 | What is the difference between Dictionary<TKey, TValue> and List<T> in terms of lookup performance? C# › Collections | C# | Collections | Beginner |
| 23 | How do you write and use a lambda expression as a shorthand for a delegate? C# › Delegates, Events & Lambdas | C# | Delegates, Events & Lambdas | Beginner |
| 24 | What are multicast delegates, and in what order do their subscribed methods get invoked? C# › Delegates, Events & Lambdas | C# | Delegates, Events & Lambdas | Intermediate |
| 25 | How do you chain multiple extension methods together in a fluent style, and what design principle makes this possible? C# › Extension Methods | C# | Extension Methods | Intermediate |
| 26 | How do the built-in Func<>, Action<>, and Predicate<T> generic delegate types differ, and when would you use each? C# › Delegates, Events & Lambdas | C# | Delegates, Events & Lambdas | Advanced |
| 27 | How does structural (deep) equality for collections work, and why doesn't List<T>.Equals() perform element-by-element comparison by default? C# › Equality: Equals, GetHashCode & IEquatable | C# | Equality: Equals, GetHashCode & IEquatable | Advanced |
| 28 | How would you implement infinite lazy sequence generation using yield return, and why is this safe despite never 'finishing'? C# › Iterators & yield return | C# | Iterators & yield return | Advanced |