How do you implement a thread-safe Singleton in .NET?

Short answer: One common thread-safe implementation uses lazy initialization with Lazy<T>: public sealed class Singleton

Example code

{
private static readonly Lazy<Singleton> instance = new
Lazy<Singleton>(() => new Singleton());
private Singleton() { }
public static Singleton Instance => instance.Value;
} This approach ensures thread safety and lazy initialization without locks.

Real-world example (ShopNest)

ShopNest payment fees use Strategy: IFeeCalculator with UPI/Card implementations chosen at runtime.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.