C# Interview Questions

Q1.cs

using System;

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

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

Q3.cs

using System;

public class Program
{
	public static void Main()
	{
		var circle1 = new Circle {
			Radius = 1
		};
		
		// Given an instance of the Circle class
		// Write code to calculate the circumference of the circle (2 * pi * r)
		// without modifying the Circle class itself.
		
	}
}

public sealed class Circle
{
	public double Radius { get; set; }

	public double Calculate(Func<double, double> op)
	{
		return op(Radius);
	}
}

Q4.cs

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

using System;
using System.Threading.Tasks;

public class Program
{
	private static string _result = "Nothing";
	
	public static void Main()
	{
		SaySomethingAsync();
		Console.WriteLine(_result);
	}

	public static async Task<string> SaySomethingAsync()
	{
		await Task.Delay(5);
		_result = "Something";
		return "SaySomething exited";
	}
}

// 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.

using System;
using System.Collections.Generic;

public class Program
{
	public static void Main()
	{
		var printers = new List<Action>();
		
		for (int i = 0; i < 10; i++)
		{
			printers.Add(() => Console.WriteLine(i));
		}

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

Q6.cs

using System.Linq;
public class Program
{
	public static void Main()
	{
        int[] numbers = { 30, 325, 18, 92, 100, 42, 72 };
        
        // Use linq to find which numbers are evenly divisible by 5.
        
    }
}

Q7.cs

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

using System;

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

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

      var tim = joe;
      tim.Name = "tim";

      Console.WriteLine(joe.Name);
      Console.WriteLine(tim.Name);
      
      var myNumber = 666;
      DoSomething(myNumber);

      Console.WriteLine(myNumber);
   }

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

Q8.cs

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

using System;

public class Program
{
	public static void Main()
	{
		try
		{
			throw new Exception("Exception 1");
		}
		catch (Exception ex)
		{
			Console.WriteLine(ex.Message);
		}

		try
		{
			throw new ApplicationException("Exception 2");
		}
		catch (ApplicationException ex)
		{
			Console.WriteLine("ApplicationException 2");
		}
		catch (Exception ex)
		{
			Console.WriteLine(ex.Message);
		}
		finally
		{
			Console.WriteLine("Finally");
		}
	}
}