186 words (approximately 1 min)

ref Structs

Instances of a ref struct are allocated on the stack and cannot escape to the managed heap.

Restrictions:

  • A ref struct cannot implement interfaces
  • A ref struct cannot be a type argument
  • A ref struct variable cannot be captured via lambda expression or local function
  • A ref struct variable cannot be used in an async method (but can be used in a synchronous method that return Task/Task<T>)

disposable

A ref struct can be made disposable: create an instance or extension Dispose method that is accessible, parameterless, and returns void.

ref Fields

ℹ️ Important

Availability: C# 11

⚠️ May hold null. Use Unsafe.IsNullRef<T>(T) to determine if a ref field is null.

ref readonly

The readonly modifier affects the expression to its right:

ref readonly int someVar; // someVar cannot receive a new value.
readonly ref int someVar; // someVar cannot refer to another object.
readonly ref readonly int someVar; // someVar cannot receive a new value and cannot receive refer to another object.

scoped ref

ℹ️ Important

Availability: C# 11

Adding the scoped modifier asserts that code will not extend the lifetime of a variable.