C# and .NET mock test: free online practice

What does the C# and .NET mock test cover?

The test covers 12 topics across three levels. Each attempt picks 15 to 30 questions at random, by the level you choose, so every attempt is different.

• ASP.NET Core and Middleware
• C# Basics and Types
• OOP and Interfaces
• Value and Reference Types
• Collections and Generics
• LINQ
• Async and Await
• Dependency Injection
• Entity Framework Core
• Memory and GC
• Delegates, Events and Lambdas
• Exceptions

Sample C# and .NET mock test questions

One question from each level, the way they appear in the test. A new set comes on the 1st of every month. Try it, then open the answer.

1. FresherDelegates, Events and Lambdas

   What does this program print?

   int x = 10;
   Func<int> twice = () => x * 2;
   x = 25;
   Console.WriteLine(twice());

   • 35
   • 20
   • 50
   • It does not compile
   Show the answer

   Answer: 50. A lambda captures the variable x itself, not a snapshot of its value. The body runs only when twice() is called, after x has become 25, so the result is 25 * 2 = 50.

2. Intermediate (1-5 years)LINQ

   What does this program print?

   var list = new List<int> { 1, 2, 3 };
   var big = list.Where(n => n > 1);
   list.Add(4);
   list.Add(5);
   Console.WriteLine(big.Count());

   • 4
   • 5
   • 2
   • 3
   Show the answer

   Answer: 4. Where is deferred: big stores the query, not its results. It runs when Count() enumerates it, after 4 and 5 were added, so it finds 2, 3, 4 and 5. Calling ToList() before the Adds would freeze the result at 2.

3. Experienced (5+ years)Exceptions

   Why is catch (Exception ex) when (Log(ex)), with Log always returning false, a useful logging trick?

   • The filter runs before the stack unwinds, so it logs with full context and the exception continues untouched
   • It runs only after every inner finally block has finished, so the log shows the state after all cleanup has run
   • It catches the exception and rethrows it with a new stack trace
   • It makes the exception non-fatal
   Show the answer

   Answer: The filter runs before the stack unwinds, so it logs with full context and the exception continues untouched. Filters run in the first pass of exception handling, before inner finally blocks and before unwinding. Returning false means not handled here, so the exception keeps its stack and a debugger still stops at the throw.

Take the full C# and .NET mock test: 15 to 30 questions and 15 to 30 minutes, by level.

How is the C# and .NET mock test scored?

A question counts as right only when you pick exactly the right option, or all the right options where it says so; a question left blank counts as wrong. Your score is the share of the test's questions you got right (15 to 30, by level). The result also scores every topic, so you know what to revise before the interview.

• 75% or more in a topica strength
• 50% to 74%worth a revision
• Under 50%a topic to work on