C# Interview Questions

Q1.cs

// What is the output of the short program below? Explain your answer.

class Program {
  static string location = default(string);
  static DateTime time = default(DateTime);
 
  static void Main() {
    Console.WriteLine(location == null ? "location is null" : location);
    Console.WriteLine(time == null ? "time is null" : time.ToString());
  }
}

Q3.cs

// Given an instance circle of the following class:

public sealed class Circle {
  public double Radius { get; set; }
  
  public double Calculate(Func<double, double> op) {
    return op(Radius);
  }
}

// Write code to calculate the circumference of the circle (2 * pi * r), without modifying the Circle class itself.

Q4.cs

// What is the output of the program below? Explain your answer.

class Program {
  private static string _result;
 
  static void Main() {
    SaySomethingAsync();
    Console.WriteLine(_result);
  }
 
  static async Task<string> SaySomethingAsync() {
    await Task.Delay(5);
    _result = "Hello world!";
    return "Something";
  }
}

// Also, would the answer change if we were to replace await Task.Delay(5); with Thread.Sleep(5)? Why or why not?

Q5.cs

// What is the output of the program below? Explain your answer.

delegate void Printer();

static void Main()
{
      List printers = new List();
      for (int i = 0; i < 10; i++)
      {
           printers.Add(delegate { Console.WriteLine(i); });
      }

      foreach (var printer in printers)
      {
           printer();
      }
}

Q6.cs

using System.Linq;

static void Main(string[] args)
{
    int[] numbers = { 30, 325, 18, 92, 100, 42, 72 };
}

// Use linq to find which numbers are evenly divisible by 5.

Q7.cs

public class Person
{
   public string Name { get; set; }
}

public class Program
{
   public static void Main(string[] args)      
   {
      Person joe = new Person();
      joe.Name = "Joe";

      Person tim = joe;
      tim.Name = "tim";

      Console.WriteLine(joe.Name);
      Console.WriteLine(tim.Name);

      
      int myNumber = 666;
      DoSomething(myNumber);

      Console.WriteLine(myNumber);
   }

   private static void DoSomething(int someNumber)
   {
      someNumber = 777;
   }
}