C# Questions & Answers on Operation with LINQ for Freshers

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1. What will be the output of the given code snippet?
  1. class Program
  2. {
  3.     static void Main(string[] args)
  4.     {
  5.         string[] strs = {"alpha", "beta", "gamma"};
  6.         var chrs = from str in strs
  7.                    let chrArray = str.ToCharArray()
  8.                    from ch in chrArray
  9.                    orderby ch
  10.                    select ch;
  11.         Console.WriteLine("The individual characters in sorted order:");
  12.         foreach (char c in chrs) 
  13.         Console.Write(c + " ");
  14.         Console.WriteLine();
  15.         Console.ReadLine();
  16.     }
  17. }
a) a a l h a b g m m a p e t a
b) a a a a a b e g h l m m p t
c) a g h l m m p t a a a a b e
d) Run time error
Answer: b
Output: a a a a a b e g h l m m p t
2.What will be the output of the given code snippet?
  1.  class Program
  2.  {
  3.      static void Main(string[] args)
  4.      {
  5.          int[] nums = { 1, -2, 3, 0, -4, 5 };
  6.          var posNums = nums.Where(n => n > 0).Select(r => r*2).OrderByDescending(r=>r);
  7.          Console.Write("The positive values in nums: ");
  8.          foreach(int i in posNums) 
  9.          Console.Write(i + " ");
  10.          Console.WriteLine();
  11.          Console.ReadLine();
  12.      }
  13.  }
a) code run successfully prints nothing
b) run time error
c) code run successfully prints multiple of 2
d) compile time error
Answer: c

Explanation: We had created the queries by using query method such as Where() and Select().This creates a query called posNums that creates a sequence of positive values in nums in descending order using the method OrderByDescending().
Output: 10 6 2
3. What will be the output of the given code snippet?
  1.  class Program
  2.  {
  3.      static void Main(string[] args)
  4.      {
  5.          int[] nums = {3, 1, 2, 5, 4};
  6.          var ltAvg = from n in nums
  7.                      let x = nums.Average()
  8.                      where n < x
  9.                      select n;
  10.          Console.WriteLine("The average is " + nums.Average());
  11.          Console.ReadLine();
  12.      }
  13.  }
a) Run time error
b) 3
c) 5
d) Compile time error
Answer: b
Explanation: Built in method Avg() is used
Output: 3
4. What will be the output of the given code snippet?
  1. class Program
  2. {
  3.     static void Main(string[] args)
  4.     {
  5.         Expression<Func<int, int, bool>>
  6.         IsFactorExp = (n, d) => (d != 0) ? (n % d) == 0 : false;
  7.         Func<int, int, bool> IsFactor = IsFactorExp.Compile();
  8.         if (IsFactor(10, 5))
  9.         Console.WriteLine("5 is a factor of 10.");
  10.         if (!IsFactor(343, 7))
  11.         Console.WriteLine("7 is not a factor of 10.");
  12.         Console.ReadLine();
  13.     }
  14. }
a) Compile time error
b) Run time error
c) 5 is a factor of 10
7 is not a factor of 10
d) 5 is a factor of 10
Answer: d

Explanation: The current program has introduced the concept of expression tree.An expression tree is a representation of a lambda expression as data.The program illustrates the two key steps in using an expression tree. First, it creates an
expression tree by using this statement:
Expression>
IsFactorExp = (n, d) => (d != 0) ? (n % d) == 0 : false;
Second, this constructs a representation of a lambda expression in memory.
Output: 5 is a factor of 10
5. Choose the namespace in which Expression trees are encapsulated:
a) System.Linq
b) System.Linq.Expressions
c) System.Text
d) System.Collections.Generic
Answer: b
Explanation: By definition.
6. For the given set of codes, which query will work according to the set of code?
  1. class Program
  2. {
  3.     static void Main(string[] args)
  4.     {
  5.         int[] nums = { 1, -2, 3, 0, -4, 5 };
  6.         int len = /*_________________ */
  7.         Console.WriteLine("The number of positive values in nums: " + len);
  8.         Console.ReadLine();
  9.     }
  10. }
a) from n in nums where n > 0
select n
b) from n in nums where n > 0
select n.Count()
c) (from n in nums where n > 0
select n).Count();
d) Both b & c
Answer: c
Output: int len = (from n in nums where n > 0
select n).Count();
7. For the given set of code, what does the output represent?
  1. class Program
  2. {
  3.     static void Main(string[] args)
  4.     {
  5.         int[] nums = { 1, -2, 3, 0, -4, 5 };
  6.         var posNums = from n in nums
  7.                       where n > 0
  8.                       select n;
  9.         int len = posNums.Count();
  10.         Console.WriteLine(len);
  11.         Console.ReadLine();
  12.     }
  13. }
a) Execution of code with nothing being printed
b) Execution of code with printing all numbers
c) Execution of code with counting total numbers greater than zero
d) Run time error
Answer: c
Output: 3
8. For the given set of codes, what is the output?
  1.  class Program
  2.  {
  3.      static void Main(string[] args)
  4.      {
  5.          int[] nums = { 1, -2, 3, 0, -4, 5 };
  6.          var posNums = nums.Where(n => n < 10).Select(r => r%3);
  7.          Console.Write("The values in nums: ");
  8.          foreach (int i in posNums) Console.Write(i + " ");
  9.          Console.WriteLine();
  10.          Console.ReadLine();
  11.      }
  12.  }
a) Compile time error
b) Run time error
c) 1 -2 0 0 -1 2
d) 2 -1 0 0 -2 1
Answer: c

Explanation: Query solved using lambda expression .The code “var posNums = nums.Where(n => n < 10).Select(r => r%3)” creates a query called posNums that creates a sequence of the values less than 10 in nums.
Output: 1 -2 0 0 -1 2
9. For the given set of codes, what is the output?
  1. class Program
  2. {
  3.     static void Main(string[] args)
  4.     {
  5.         string[] strs = { ".com", ".net", "facebook.com", "google.net", "test", "netflix.net", "hsNameD.com" };
  6.         var netAddrs = from addr in strs
  7.                        where addr.Length > 4 && addr.EndsWith(".net",
  8.                        StringComparison.Ordinal)
  9.                        select addr;
  10.         foreach (var str in netAddrs) Console.WriteLine(str);
  11.         Console.ReadLine();
  12.     }
  13. }
a) Compile time error
b) Run time error
c) facebook.com
netflix.net
google.net
d) google.net
netflix.net
Answer: d

Explanation: Searches for the string which ends with .net.
Output: google.net
netflix.net
10. For the given set of codes, what is the output?
  1. class Program
  2.     {
  3.         static void Main(string[] args)
  4.         {
  5.  
  6.             int[] nums = { 1, -2, -3, 5 };
  7.             var posNums = from n in nums
  8.                           orderby n descending
  9.                           select n*4 / 2;
  10.             Console.Write("The values in nums: ");
  11.             foreach (int i in posNums) Console.Write(i + " ");
  12.             Console.WriteLine();
  13.             Console.ReadLine();
  14.         }
  15.     }
a) 10 2 -4 -6
b) 5 1 -2 -3
c) 1 5 -2 -3
d) Run time error
Answer: a
Output: 10 2 -4 -6
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