013 LINQ Count

Return number of item the IEnumerable collection.Returns 0 if there is no item in the collection.Count can be calculated for both LINQ query and Lambda expression.


1) Below is example of count example with LINQ query on a array.
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using System;

using System.Collections.Generic;

using System.Data.SqlClient;

using System.Data.Sql;

using System.Data;

using System.Linq;

using System.Collections;

using System.Xml;

using System.Xml.Linq;

using System.IO;

namespace ConsoleApplication1

{

              class Program

              {

                     static void Main(string[] args)

                      {

                         int[] marks = { 10, 20, 30, 40, 50, 60 };

                         int sumOfMarks = (from x in marks select x).Count();

                         Console.WriteLine("The Count is :" + sumOfMarks.ToString());

                         Console.ReadKey();

                    }

           }

}

//The Count is :6

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2) Below is example of count example with LINQ query on a collcetion.
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using System;

using System.Collections.Generic;

using System.Data.SqlClient;

using System.Data.Sql;

using System.Data;

using System.Linq;

using System.Collections;

using System.Xml;

using System.Xml.Linq;

using System.IO;

namespace ConsoleApplication1

{

             class Program

             {

                    static void Main(string[] args)

                    {

                            IList<student> myList = new List<student>()

                            {

                              new student { name = "John1", roll = 121, age = 5 },

                              new student { name = "John2", roll = 122, age = 6 },

                              new student { name = "John3", roll = 123, age = 7 },

                              new student { name = "John4", roll = 124, age = 8 },

                              new student { name = "John5", roll = 125, age = 9 },

                              new student { name = "John6", roll = 126, age = 10 },

                              new student { name = "John7", roll = 127, age = 11 },

                              new student { name = "John8", roll = 128, age = 17 },

                              new student { name = "John9", roll = 129, age = 18 },

                              new student { name = "John10", roll = 1210, age = 19 },

                              new student { name = "John11", roll = 1211, age = 20 }

                           };

                       var sumOfAge = myList.Count();

                      Console.WriteLine("The Age is :" + sumOfAge.ToString());

                      Console.ReadKey();

                      }

              }

}

public class student

{

            public string name { get; set; }

            public int roll { get; set; }

            public int age { get; set; }

};

//The Age is :11

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3)Below is example of count with group by example.

using System;

using System.Collections.Generic;

using System.Data.SqlClient;

using System.Data.Sql;

using System.Data;

using System.Linq;

using System.Collections;

using System.Xml;

using System.Xml.Linq;

using System.IO;

namespace ConsoleApplication1

{

           class Program

           {

              static void Main(string[] args)

               {

                        var myList = new List<student>

                                {

                                    new student { name = "John1", roll = 121, age = 5 },

                                    new student { name = "John2", roll = 122, age = 6 },

                                    new student { name = "John3", roll = 123, age = 7 },

                                    new student { name = "John4", roll = 124, age = 5 },

                                    new student { name = "John5", roll = 125, age = 9 },

                                    new student { name = "John6", roll = 126, age = 10 },

                                    new student { name = "John7", roll = 127, age = 5 },

                                    new student { name = "John8", roll = 128, age = 17 },

                                    new student { name = "John9", roll = 129, age = 5 },

                                    new student { name = "John10", roll = 1210, age = 19 },

                                    new student { name = "John11", roll = 1211, age = 20 }

                            };

                           var query = from obj in myList

                                        group obj by obj.age into countGroup

                                        select new

                                        {

                                               Name = countGroup.Key,

                                               Count = countGroup.Count(),

                                        };

                          foreach (var c in query)

                          {

                            Console.WriteLine("Name : " + c.Name + "|Count :" + c.Count);

                         }

                      Console.ReadKey();

              }

      }

}

public class student

{

         public string name { get; set; }

         public int roll { get; set; }

         public int age { get; set; }

};

Output :
Name : 5|Count :4
Name : 6|Count :1
Name : 7|Count :1
Name : 9|Count :1
Name : 10|Count :1
Name : 17|Count :1
Name : 19|Count :1
Name : 20|Count :1