Use of Value and Reference Type in .NET Core
💡 Concept Name
Value Type vs Reference Type
📘 Quick Intro
In .NET Core, value types are stored in the stack and hold actual data, while reference types are stored in the heap and hold a pointer to the data. Understanding both is key to memory management and performance.
🧠 Analogy / Short Story
Imagine two people sharing a paper document. One person gives a *copy* (value type), and the other gives a *link* to the original (reference type). With a copy, changes won’t affect the original. With a link, both see the changes in real time.
🔧 Technical Explanation
- Value Types: Directly contain data. Stored on stack. Example:
int, float, struct. - Reference Types: Store reference to data. Stored on heap. Example:
class, object, string, array. - Stack memory is faster and short-lived, heap is slower but flexible.
- Passing value types copies data; passing reference types copies reference (pointer).
🎯 Purpose & Use Case
- ✅ Value types for small, fixed data structures (e.g., coordinates, enums)
- ✅ Reference types for shared or large data (e.g., models, lists, strings)
- ✅ Use value types when mutability isn’t required
- ✅ Use reference types to share and update data across layers
💻 Real Code Example
// Value Type
int a = 5;
int b = a;
b = 10; // a is still 5
// Reference Type
class Person { public string Name; }
Person p1 = new Person() { Name = "Ravi" };
Person p2 = p1;
p2.Name = "Amit"; // p1.Name is also "Amit"
❓ Interview Q&A
Q1: What is a value type?
A: A type that holds the data directly.
Q2: Where are value types stored?
A: On the stack.
Q3: Give examples of value types.
A: int, float, bool, struct.
Q4: What is a reference type?
A: A type that stores a reference to the actual data.
Q5: Where are reference types stored?
A: On the heap.
Q6: Are strings value or reference types?
A: Reference types (but immutable).
Q7: What happens when you pass a value type to a method?
A: A copy is passed.
Q8: Do reference types support inheritance?
A: Yes.
Q9: What is boxing?
A: Converting a value type to object (reference type).
Q10: Can a struct inherit from another struct?
A: No, structs don’t support inheritance.
📝 MCQs
Q1. What is a value type stored in?
- Heap
- Stack
- Cache
- Queue
Q2. Which of these is a reference type?
- int
- bool
- struct
- string
Q3. What happens when a reference type is assigned to another?
- Copied by value
- No assignment allowed
- Both point to same memory
- It crashes
Q4. What does 'boxing' mean in .NET?
- Object to class
- Value type to reference type
- Method to function
- None of these
Q5. Which keyword is used to define a value type?
- class
- struct
- interface
- enum
Q6. Which memory is used for large or dynamic data?
- Register
- Stack
- Heap
- ROM
Q7. What happens when you pass a value type to a method?
- Reference is passed
- A copy is passed
- Pointer is passed
- Link is passed
Q8. Are classes value or reference types?
- Value
- Reference
- Hybrid
- None
Q9. Which of these types is immutable?
- int
- bool
- string
- object
Q10. Can reference types be null?
- No
- Only in C++
- Yes
- Only structs
💡 Bonus Insight
Use structs (value types) only when you need small, lightweight, immutable data. Overusing value types for large data can negatively impact performance due to copying overhead.
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