· 3 min read

Learn C# Fundamentals and .NET Core with 99 Flashcards: From Boxing and the CLR to LINQ and Async/Await

Master C# and .NET Core vocabulary with 99 real flashcards from deck JT0914 on Flip It: CLR, boxing, ref vs out, records, LINQ, async/await, plus a study order and C#-specific tips.

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Tutorials teach C# syntax; interviews test C# vocabulary: boxing, CLR, IQueryable, init-only, sealed override. Deck JT0914 — C#: Fundamentals & .NET Core on Flip It turns that vocabulary into 99 flashcards, from the Common Language Infrastructure to the null-conditional operator.

Study this deck: C#: Fundamentals & .NET Core

1 / 10
Question

C# and who created it

Knew itLearning

Tap the card for the answer · swipe right if you knew it, left if not

Ten cards to test yourself first

Cover the right column and see how many you get.

FrontBack
Boxing in C#Converting a value type to a reference type (object)
CIL or MSILCommon Intermediate Language — the bytecode that C# compiles to
var vs dynamicvar: compile-time type inference, then strongly typed. dynamic: type checking at runtime
ref vs out parametersref: must be initialized before passing. out: no initialization needed, must be assigned inside the method
Can C# have multiple inheritance?No multiple class inheritance (diamond problem); yes, multiple interface implementation
Null coalescing operator ??Returns the first non-null value: string name = input ?? "default"; — C# 8 adds ??=
IEnumerable vs IQueryableIEnumerable: in-memory, LINQ to Objects. IQueryable: expression trees, deferred execution, LINQ to SQL
Records (C# 9+)Immutable reference types: record Person(string Name, int Age);
StringBuilder vs stringstring is immutable (every change allocates); StringBuilder is a mutable buffer
Task vs ThreadThread: OS-level, heavyweight. Task: lightweight abstraction over the thread pool

Seven or more right? Skip to the async and LINQ cards. Fewer? Start from the runtime block below.

Everything the deck covers

  • Runtime and platform: C# and Anders Hejlsberg, CLI, CLR, CIL/MSIL, JIT compilation, garbage collection, .NET Framework vs .NET Core, namespaces, using directives, dependency injection in .NET Core.
  • Type system: value vs reference types, stack vs heap, boxing/unboxing, struct vs class, enums, nullable types (int?, HasValue), tuples (X: 10, Y: 20), anonymous types, var, dynamic, generics and generic constraints (where T : class).
  • OOP: inheritance, polymorphism, virtual/override, abstract vs virtual, interfaces, sealed, access modifiers, properties and auto-properties, init-only properties, indexers, operator overloading, == vs Equals().
  • Modern syntax: top-level statements (C# 9), lambdas, expression-bodied members, string interpolation, nameof, params, pattern matching, switch expressions (C# 8), is and as, ?., ??, ??=.
  • Functional and async: delegates, events, extension methods, LINQ query vs method syntax, yield, IEnumerable<T>, async/await, Task and Task<T>, lock.
  • Errors and metadata: try-catch-finally, throw vs throw ex, attributes ([Obsolete], [Serializable]), reflection.

Study order that matches the deck's structure

Useful quirk: the first 49 cards are code-heavy explanations, the last 50 are one-line definitions of the same concepts. Use that.

  1. Definitions first (cards 50-99). One-liners like Boxing = converting a value type to a reference type stick in a single session.
  2. Code cards second (cards 1-49). Now each long card attaches to a word you already know. When you flip Pattern matching (C# 7+) and see case int i when i > 0:, you are reading an example, not learning a concept.
  3. Pair the duplicates. Boxing, sealed, records, yield, is/as, attributes and extension methods each appear twice; getting both versions right on the same day means the concept is solid.

Two C#-specific tips

  • Attach a version number to every "modern" card. The deck tags them: auto-properties C# 3, pattern matching C# 7, switch expressions and ??= C# 8, records, init-only properties and top-level statements C# 9. Say the version aloud when you flip the card — it is exactly what interviewers ask.
  • Rewrite the four contrast cards as a single table. struct/class, ref/out, abstract/virtual, IEnumerable/IQueryable are all "A vs B" cards. Sketch them once as one two-column table by hand; the deck then quizzes you on a picture you already own.

Get the deck

Sign in to Flip It and open deck JT0914 (C#: Fundamentals & .NET Core) from the library. Ninety-nine cards at 15 minutes a day is roughly ten days to full coverage, with spaced repetition handling the rest.

Learning the whole managed-language family? The Java core concepts and OOP study guide covers the JVM equivalents of most cards above.

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