Readonly structs in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a readonly struct in C#?

A readonly struct is a special kind of struct where all its fields are readonly. This means once created, its data cannot be changed, making it immutable.

intermediate

Why use readonly structs instead of regular structs?

Readonly structs help avoid accidental changes to data and can improve performance by enabling the compiler to optimize code, especially when passing structs by reference.

beginner

How do you declare a readonly struct in C#?

Use the keyword readonly before struct. For example: <br>public readonly struct Point { public int X { get; } public int Y { get; } }

intermediate

Can a readonly struct have methods that modify its fields?

No. Since all fields are readonly, methods cannot change the state of the struct. Any method that tries to modify fields will cause a compile error.

beginner

What happens if you try to assign a value to a field inside a readonly struct after it is created?

The compiler will give an error because readonly structs prevent modification of their fields after creation, ensuring immutability.

How do you declare a readonly struct in C#?

A struct MyStruct readonly { }

B public struct readonly MyStruct { }

C readonly public class MyStruct { }

D public readonly struct MyStruct { }

The correct syntax places 'readonly' before 'struct': public readonly struct MyStruct { }

What is a key benefit of using readonly structs?

A They improve immutability and can optimize performance.

B They allow fields to be changed anytime.

C They make structs behave like classes.

D They allow inheritance from other structs.

Readonly structs ensure immutability and help the compiler optimize code, improving performance.

Can a readonly struct have a method that modifies its fields?

A Only if the method is static.

B No, fields cannot be modified after creation.

C Yes, always.

D Yes, but only inside constructors.

Readonly structs prevent modification of fields after creation, so methods cannot change fields.

What error occurs if you try to change a field in a readonly struct after it is created?

A Compiler error.

B Runtime exception.

C Warning only.

D No error, it works fine.

The compiler prevents modification of readonly struct fields and shows an error.

Which of these is true about readonly structs?

A They can inherit from other structs.

B They can have mutable fields.

C They are immutable after creation.

D They are reference types.

Readonly structs are immutable after creation; their fields cannot be changed.

Explain what a readonly struct is and why you might use it.

Think about how readonly structs prevent changes and help the compiler.

Describe how to declare a readonly struct and what restrictions it imposes on its fields and methods.

Focus on declaration and immutability rules.