C# (C-Sharp) Question Answers - 141-152

141. What are async and await used for?

Enable non-blocking asynchronous programming for improved responsiveness in I/O-bound operations.

142. What are delegates in C#?

Type-safe function pointers used for callbacks and event handling.

143. What is dependency injection?

A design pattern promoting loose coupling by injecting dependencies instead of hardcoding them.

144. Difference between interface and abstract class?

Interfaces define contracts; abstract classes can provide partial implementation.

145. What is a nullable type in C#?

Allows value types (e.g., int?) to represent null values.

146. What is the var keyword?

Enables implicit typing; compiler infers the type at compile time.

147. Difference between == and .Equals()?

== compares references for objects; .Equals() compares values.

148. What is LINQ?

Language Integrated Query—query collections using SQL-like syntax.

149. What is a lambda expression?

Concise way to write anonymous functions: (x) => x * x

150. What is the params keyword?

Allows passing variable number of arguments to a method.

151. Difference between IEnumerable and IQueryable?

IEnumerable executes in-memory; IQueryable builds expression trees for deferred execution (e.g., LINQ to SQL).

152. Use of Span<T> in C# 13?

Provides high-performance, memory-safe access to contiguous memory regions without allocations.