C# and .NET tricky questions

I have collected some most interesting and not well-known questions from the web. And also based on interesting books, articles and videos I have seen, I have wrote some of questions myself.
I want propose you to guess right answer.


1. What would be displayed? (if something would be displayed at all)

string nullString = (string)null;
Console.WriteLine (nullString is string);

2. What would be displayed on the screen in .NET console application?

Console.WriteLine (Math.Round(1.5));
Console.WriteLine (Math.Round(2.5));

3. What would be the result of

static void Main(string[] args)
{
    float f = Sum(0.1f, 0.2f);
    float g = Sum(0.1f, 0.2f);
    Console.WriteLine(f == g);
}

static float Sum(float f1, float f2)
{
    return f1 + f2;
}

a) True
b) False
c) Exception would be thrown
d) That depend (could be either true or false)



4. What would be the result of

float price = 4.99F;
int quantity = 17;
float total = price * quantity;
Console.WriteLine("The total price is ${0}.", total);

a) The total price is $85
b) The total price is $84.83
c) The total price is $84
d) The total price is $84.82999



5. What is the right way to store passwords in database? Choose one or multiple correct answers

a) In plain text
b) Encrypted with DES
c) Encrypted with AES
d) Hashed with MD5
e) Hashed with SHA512



6. In between different .NET technologies there is a lot of timers. Which one timer does not exist?

a) Timer from System.Windows.Forms
b) DispatchTimer from System.Windows.Threading
c) DispatchTimer from Windows.UI.XAML
d) Timer from System.Timers
e) Timer from System.Windows.Threading.Timers
f) Timer from System.Threading



7. Which one .NET REPL does not exists?

a) dotnetfiddle.net
b) repl.it/languages/csharp
c) csharpcompiler.net
d) dotnet.microsoft.com/platform/try-dotnet
e) csharppad.com



8. If you want to set a type long for a number in C# you can add at the end letter L or l. For example:

var l = 138l;

With which letter it is possible to mark a decimal type?

a) C or c
b) D or d
c) M or m
d) E or e



9. What will display on the screen console application that will contain next code:

     class Program
    {
         static Program()
        {
            Console.WriteLine("Static constructor");
        }

         public Program()
        {
            Console.WriteLine("Constructor");
        }

        static void Main(string[] args)
        {
            Console.WriteLine("Main");
            Console.ReadLine();
        }
    }

10. What would be displayed as result?

      [Flags]
      public enum Status 
      {
         Funny = 0x01,
         Hilarious = 0x02,
         Boring = 0x04,
         Cool = 0x08,
         Interesting = 0x10,
         Informative = 0x20,
         Error = 0x40
      }

  public static void Main (string[] args) {
         var code = 24;
         Console.WriteLine (String.Format("This Quiz is: {0}",  (Status)code));
      }

11. Where is a difference between String and string?



12. What does mean (or at least has meant initially) Visual Studio sign?



13. Please match:
Async/await
Try/catch
ValidateAntiForgeryToken
with abbreviations:
TAP, SEH, STP



14. Which one is not .NET CMS?

a) mojoPortal
b) N2 CMS
c) Atomic CMS
d) Composite C1
e) Concrete5
f) Piranha CMS



15. What would be displayed on the screen?

  
     class Program
    {
        private static int y = x;
        private static int x = 5;

        static void Main(string[] args)
        {
            Console.WriteLine(y);
            Console.ReadLine();
        }
    }

16. Which Concurrent Collection class is missing in .Net

a) ConcurrentQueue
b) ConcurrentStack
c) ConcurrentList
d) ConcurrentDictionary
e) ConcurrentBag



17. What is the preferable way to run async code synchronously (if it’s not possible to use await):

a) Wait()
b) Result()
c) GetAwaiter().GetResult()