C#

Value types against reference types, collections, interfaces and LINQ — the fundamentals behind every .NET job posting.

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In this course

Value types, reference types, and nullWhat actually gets copied when you pass an int against a List, and how a value type opts into null.7 min
Classes, properties, and interfacesAuto-properties instead of hand-written getters, interfaces as contracts, and the difference between override and new.8 min
Collections and LINQList and Dictionary, and the Where/Select/OrderBy chain that replaces a hand-written loop.8 min
Exceptions, and catching the type you actually expecttry/catch/finally, catching specific types first, and why swallowing an exception is worse than not catching it.7 min
Generics and constraintsWriting one method that works for any type, without losing the type back out.7 min
Equality, GetHashCode and hashed collectionsWhat == and Equals compare for classes, strings and boxed values, and why Equals without GetHashCode breaks every HashSet.9 min
Records and immutabilityPositional records, value equality you get for free, with-expressions, and why a record holding a List is only shallowly immutable.8 min
Structs, copies and boxingWhere a struct gets silently copied — into a box, out of a List, through a readonly field — and why default(T) skips your constructor.9 min
Pattern matching and nullable reference typesSwitch expressions with type, property, relational and list patterns, and what nullable reference types do and do not protect you from.9 min
Delegates, lambdas and closuresFunc, Action and method groups, what a lambda captures, and the for-loop capture that still catches people out.8 min
EventsWhat the event keyword adds to a delegate, raising safely with ?.Invoke, unsubscribing correctly, and what a throwing handler does to the rest.8 min
Deferred execution, iterators and IQueryableHow a LINQ pipeline pulls one element at a time, why enumerating twice runs everything twice, and what changes when the source is an IQueryable.10 min
async, await and TaskWhat an async method does before its first await, where its exceptions go, and how starting tasks differs from awaiting them.9 min
Deadlocks, ConfigureAwait and ValueTaskWhy blocking on async code can hang forever, what ConfigureAwait(false) changes and when it does not help, and the rules ValueTask comes with.11 min
IDisposable, using, and what the GC does not doWhy the garbage collector frees memory but not files or connections, how using guarantees Dispose, and the generational GC in a few facts.9 min
Strings, StringBuilder and Span<T>Immutable strings, ordinal against culture-aware comparison, building text without quadratic copying, and slicing memory with Span<T> instead of copying it.10 min