Adaptive skill practice — find your level, get sharper.

C# practice

LINQ, async/await, records, and the CLR model

Modern C# and the .NET runtime model, from Microsoft’s official documentation. Value versus reference types (structs, classes, boxing), nullable reference types, properties and init-only setters, records and value equality, pattern matching (switch expressions, property patterns), LINQ (deferred execution and its traps), delegates, events and lambdas, generics with constraints and variance, async/await done right (Task vs ValueTask, the sync-over-async deadlock), exceptions and filters, interfaces (default members, explicit implementation), inheritance and polymorphism (virtual/override/new), and collections and spans. Predict-the-output and spot-the-bug items throughout; every explanation names the principle, the trap, and a rule. Authored to the current stable .NET release.

• Meets you at your level — never too easy, never too hard.

• Adapts every question to how you’re doing.

• Tracks your level over time. Skill practice, not a test.

New here? Read the C# guide

A free 18-minute primer — the mental model, the mistakes beginners make, and what to practise first.

Curriculum

221 concepts across 26 chapters, from foundations through advanced practice — each one a concept the adaptive question bank can teach and test.

A. The type system: value types, reference types, boxing

B. Numbers and arithmetic

C. Strings and text

D. Null: nullable value types and nullable reference types

E. Structs and value semantics

F. Records and immutable data

G. Members: fields, properties, constructors, indexers

H. Inheritance and polymorphism

I. Interfaces

J. Methods, parameters and overloads

K. Operators and expressions

L. Statements and control flow

M. Pattern matching

N. Exceptions

O. Generics

P. Variance

Q. Delegates, lambdas and events

R. Collections

S. Iterators

T. LINQ

U. Asynchronous programming

V. Resource management and the garbage collector

W. Spans, memory and allocation

X. Reflection, attributes and unsafe code

Y. Namespaces and using directives

Z. Tuples and deconstruction

View the full curriculum →

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