What is a custom exception?
💡 Concept: Custom Exception
A custom exception in C# is a user-defined exception class derived from System.Exception to represent specific error conditions unique to an application.
📘 Quick Intro
Creating custom exceptions allows developers to provide more meaningful error information and better error handling tailored to business logic.
🧠 Analogy
Think of custom exceptions as custom warning lights on a car dashboard that indicate specific issues unique to your vehicle model.
🔧 Technical Explanation
- 📦 Custom exception classes inherit from System.Exception or its subclasses.
- 📝 Override constructors to provide custom messages or inner exceptions.
- 🔍 Enables catching and handling application-specific errors distinctly.
- ⚙️ Improves clarity and maintainability of error handling logic.
- 🔒 Follow .NET guidelines for naming and serialization support.
🎯 Use Cases
- ✅ Represent domain-specific errors like validation failures.
- ✅ Encapsulate error details not covered by standard exceptions.
- ✅ Facilitate cleaner error handling in layered architectures.
- ✅ Provide custom error messages and recovery actions.
💻 Code Example
public class InvalidUserInputException : Exception {
public InvalidUserInputException() { }
public InvalidUserInputException(string message)
: base(message) { }
public InvalidUserInputException(string message, Exception inner)
: base(message, inner) { }
}
❓ Interview Q&A
Q1: What is a custom exception?
A: A user-defined exception class for specific error conditions.
Q2: Why create custom exceptions?
A: To represent domain-specific errors clearly.
Q3: From which class do custom exceptions inherit?
A: System.Exception.
Q4: How to add custom messages?
A: Override constructors with message parameters.
Q5: Can custom exceptions have inner exceptions?
A: Yes, for chaining errors.
Q6: Are custom exceptions mandatory?
A: No, but recommended for clarity.
Q7: How do custom exceptions improve error handling?
A: By providing specific context.
Q8: Should custom exceptions be serializable?
A: Yes, for remoting and logging.
Q9: Can you catch custom exceptions specifically?
A: Yes, like any exception type.
Q10: What naming convention is recommended?
A: Suffix with 'Exception'.
📝 MCQs
Q1. What is a custom exception?
- System exception
- User-defined exception class
- Runtime error
- Syntax error
Q2. Why create custom exceptions?
- Avoid errors
- Represent specific errors
- Ignore errors
- Crash program
Q3. From which class to inherit?
- System.Object
- System.Exception
- System.Error
- System.Runtime
Q4. Can custom exceptions have inner exceptions?
- No
- Yes
- Sometimes
- Never
Q5. Are custom exceptions mandatory?
- Yes
- No
- Sometimes
- Always
Q6. How do custom exceptions improve error handling?
- Hide errors
- Provide context
- Ignore errors
- Log errors
Q7. Should custom exceptions be serializable?
- No
- Yes
- Maybe
- Never
Q8. Can you catch custom exceptions specifically?
- No
- Yes
- Sometimes
- No idea
Q9. What naming convention is recommended?
- Prefix 'Error'
- Suffix with 'Exception'
- No convention
- Use abbreviations
Q10. How to add custom messages?
- Use attributes
- Override constructors
- Use interfaces
- Throw exceptions
💡 Bonus Insight
Defining custom exceptions helps create more maintainable and understandable error handling strategies aligned with business needs.
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