What are Auto-Implemented Properties in C#?
💡 Concept: Auto-Implemented Properties
Auto-implemented properties allow you to declare a property without writing explicit code for the backing field. The compiler handles the hidden field, reducing boilerplate and improving readability.
📘 Quick Intro
Auto-implemented properties simplify property declarations. Instead of manually creating private fields and writing logic-less getters and setters, you let the compiler do it with just { get; set; }.
🧠 Analogy
Think of an auto-implemented property like ordering food online. You don’t need to know who’s cooking (backing field)—you just make the request and receive the dish (value). It abstracts away the inner process.
🔧 Technical Explanation
- 🔹 Auto-properties use an implicit, compiler-generated private backing field.
- 🔹 Syntax:
public string Name { get; set; } - 🔹 You can make them read-only by omitting the
setaccessor. - 🔹 You can initialize them directly (e.g.,
{ get; set; } = "Default";). - 🔹 You can also use
initinstead ofsetfor immutability after construction (C# 9+).
🎯 Use Cases
- ✅ For data models and DTOs where minimal logic is needed.
- ✅ In MVVM patterns for clean binding properties.
- ✅ To reduce boilerplate when no validation is required.
- ✅ In ASP.NET Core models for form data binding.
💻 Code Example
public class Product
{
// Auto-implemented properties
public string Name { get; set; }
public decimal Price { get; set; } = 0.0m;
// Read-only auto-property
public DateTime CreatedAt { get; } = DateTime.Now;
// Init-only property (C# 9+)
public string Category { get; init; }
}
❓ Interview Q&A
Q1: What is an auto-implemented property?
A: A property where the compiler generates a private backing field automatically.
Q2: Why are auto-properties useful?
A: They reduce code verbosity and improve readability.
Q3: Can you assign default values?
A: Yes, via initialization syntax like { get; set; } = "Default";
Q4: Are auto-properties part of the public API?
A: Yes, the getters and setters are accessible according to their access modifiers.
Q5: What is an init-only property?
A: A property that can only be set during object initialization (C# 9+).
Q6: Can you use private setters?
A: Yes, e.g., public string Name { get; private set; }.
Q7: Can you override auto-properties?
A: No, properties must be explicitly virtual to allow overrides.
Q8: Are auto-properties serialized?
A: Yes, most serializers work with them directly.
Q9: Are auto-properties thread-safe?
A: Not inherently; thread-safety must be handled manually.
Q10: What is the default value of an auto-property?
A: It is the default value for its type (e.g., null for reference types).
📝 MCQs
Q1. What does an auto-property eliminate?
- Constructors
- Inheritance
- Explicit backing field
- Interfaces
Q2. Which syntax defines an auto-property?
- { get; set; }
- { set; only }
- delegate()
- void get()
Q3. What version introduced init-only setters?
- C# 6
- C# 7
- C# 8
- C# 9
Q4. Can auto-properties have private setters?
- No
- Only in classes
- Yes
- Only for fields
Q5. What is the default value of an auto-property of type int?
- null
- 0
- undefined
- empty
Q6. What is the role of the compiler in auto-properties?
- It adds validation
- It adds logs
- It generates the backing field
- Nothing
Q7. Can you use auto-properties with interfaces?
- No
- Yes
- Only with abstract classes
- Only with records
Q8. Can auto-properties be static?
- No
- Yes
- Only for fields
- Only for strings
Q9. Can an auto-property be readonly?
- No
- Yes, using get only
- Only with init
- Only with virtual
Q10. Which scenario is ideal for auto-properties?
- Complex logic
- Deep inheritance
- Simple data models
- Abstract classes
💡 Bonus Insight
Auto-properties streamline your code and help express your intent more clearly. They pair well with records and DTOs and are a great fit for most use cases where business logic isn't embedded in accessors.
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