Count

In this chapter you will learn:

How to count with count operator
Count with filter delegate
supply a predicate
Count with string operator
Count distinct values

How to count with count operator

Count simply enumerates over a sequence, returning the number of items:

using System;//from ja  v  a 2 s. c o m
using System.Collections;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        int fullCount = new int[] { 5, 6, 7 }.Count();  // 3

        Console.WriteLine(fullCount);

    }
}

The output:

Count with filter delegate

using System;/*from j  av a  2 s  . c o m*/
using System.Collections.Generic;
using System.Linq;
using System.Text;

public class MainClass {
    public static void Main() {
        int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

        int oddNumbers = numbers.Count(n => n % 2 == 1);

        Console.WriteLine("There are {0} odd numbers in the list.", oddNumbers);
    }
}

supply a predicate

You can optionally supply a predicate:

using System;/*from  j  a  v  a  2  s. c  o m*/
using System.Collections;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        int digitCount = "java2s.com".Count(c => char.IsDigit(c)); 
        
        Console.WriteLine(digitCount);
    
    }
}

Count with string operator

using System;//  j  a  va 2  s .c o m
using System.Linq;
using System.Collections;
using System.Collections.Generic;

public class MainClass {
    public static void Main() {
        string[] presidents = {"java", "Java", "a", "H", "java2s.com", "Jack"};

        int count = presidents.Count(s => s.StartsWith("j"));
        Console.WriteLine(count);

    }
}

Count distinct values

using System;// j  a v  a2 s. com
using System.Collections.Generic;
using System.Linq;
using System.Text;

public class MainClass {
    public static void Main() {
        int[] factorsOf300 = { 2, 2, 3, 5, 5 };

        int uniqueFactors = factorsOf300.Distinct().Count();

        Console.WriteLine("There are {0} unique factors of 300.", uniqueFactors);
    }
}

Next chapter...

What you will learn in the next chapter: