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Details: Written by Stanko Milosev; Category: C#; Published: 09 August 2018; Hits: 87

One example to find out number of years of oldest child in a list of parents.

using System;
using System.Collections.Generic;
using System.Linq;

namespace LINQtest
{

    public class Child
    {
        public int Age { get; set; }
    }

    public class Parent
    {
        public Child[] Kids { get; set; }
    }

    public class MyLinq
    {
        public List<Parent> Parents { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Parent parentOne = new Parent();
            parentOne.Kids = new Child[2];

            parentOne.Kids[0] = new Child();
            parentOne.Kids[0].Age = 1;

            parentOne.Kids[1] = new Child();
            parentOne.Kids[1].Age = 2;

            Parent parentTwo = new Parent();
            parentTwo.Kids = new Child[3];
            parentTwo.Kids[0] = new Child();
            parentTwo.Kids[0].Age = 5;
            parentTwo.Kids[1] = new Child();
            parentTwo.Kids[1].Age = 7;
            parentTwo.Kids[2] = new Child();
            parentTwo.Kids[2].Age = 6;

            Parent parentThree = new Parent();
            parentThree.Kids = new Child[2];
            parentThree.Kids[0] = new Child();
            parentThree.Kids[0].Age = 3;

            parentThree.Kids[1] = new Child();
            parentThree.Kids[1].Age = 4;

            MyLinq myLinq = new MyLinq();
            myLinq.Parents = new List();
            myLinq.Parents.Add(parentOne);
            myLinq.Parents.Add(parentTwo);
            myLinq.Parents.Add(parentThree);

            int maxAge = myLinq.Parents.Max(parent => parent.Kids.Max(kid => kid.Age));

            Console.WriteLine("Oldest kid is age of: " + maxAge);
            Console.WriteLine("Press any key");
            Console.ReadKey();
        }
    }
}

POI:

int maxAge = myLinq.Parents.Max(parent => parent.Kids.Max(kid => kid.Age));

Because for example code:

IEnumerable<int> maxAges = myLinq.Parents.Select(parent => parent.Kids.Max(kid => kid.Age));

Will return collection of ages in list of parents.

Details: Written by Stanko Milosev; Category: C#; Published: 17 September 2017; Hits: 1730

One my example of interpolated string (taken from here):

string name = "stanko";
DateTime hours = DateTime.Now;
Console.WriteLine($"Name = {name}, hours = {hours:hh}");
Console.ReadKey();

Composite string:

string name = "stanko";
Console.WriteLine("Name = {0}, hours = {1:hh}", name, DateTime.Now);
Console.ReadKey();

According to Microsoft:

Interpolated string are easier to understand than a composite format string.

Details: Written by Stanko Milosev; Category: C#; Published: 17 September 2017; Hits: 1869

To assign IEnumerable to a new instance of IEnumerable, you will need ToList method. Here is an example:

IEnumerable instanceOne;
IEnumerable instanceTwo;

List instanceListOne = new List();

instanceListOne.Add("a");
instanceListOne.Add("b");

instanceOne = instanceListOne;
instanceTwo = instanceOne;

instanceListOne.Add("c");

foreach (string instance in instanceTwo)
{
	Console.WriteLine(instance);
}

Console.WriteLine("Press any key");
Console.ReadKey();

instanceTwo = instanceOne.ToList();
instanceListOne.Add("d");

foreach (string instance in instanceTwo)
{
	Console.WriteLine(instance);
}

Console.WriteLine("Press any key");
Console.ReadKey();

Notice first:

instanceListOne.Add("a");
instanceListOne.Add("b");

instanceOne = instanceListOne;
instanceTwo = instanceOne;

Then:

instanceListOne.Add("c");

I added firs "a" and "b" to instanceListOne, I assigned instanceListOne to instanceOne, and then I assigned instanceOne to instanceTwo, after that I added "c" to instanceListOne, then I went through instanceTwo and result is:

"c" is displayed also in instanceTwo.

Now to have two separate instances of IEnumerable, we need something like:

instanceTwo = instanceOne.ToList();

After that I did something like:

instanceListOne.Add("d");

Result will be still as in previous picture, "d" is not added to instanceTwo, since now we really have separate instances.

Example download from here.

Details: Written by Stanko Milosev; Category: C#; Published: 06 September 2017; Hits: 1842

IComparer example, with numbers first, and empty strings at the end:

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

namespace IComparer
{
    class Program
    {
        public class myCaseInsensitiveComparer : IComparer
        {
            public int Compare(string x, string y)
            {
                bool isXnumeric = int.TryParse(x, out var xInt);
                bool isYnumeric = int.TryParse(y, out var yInt);

                if (string.IsNullOrWhiteSpace(x) && string.IsNullOrWhiteSpace(y))
                {
                    return 0;
                }

                if (string.IsNullOrWhiteSpace(x))
                {
                    return 1;
                }

                if (string.IsNullOrWhiteSpace(y))
                {
                    return -1;
                }

                if (isXnumeric && isYnumeric)
                {
                    return xInt.CompareTo(yInt);
                }

                return string.Compare(x, y, StringComparison.OrdinalIgnoreCase);
            }
        }

        static void Main(string[] args)
        {
            string[] words = { "1", "a", "A", "", "b", "", "B", "C", "c", "", "", "3" };
            IOrderedEnumerable sortedWords = words.OrderBy(a => a, new myCaseInsensitiveComparer());

            foreach (var sortedWord in sortedWords)
            {
                Console.WriteLine(sortedWord);
            }

            Console.WriteLine("Press any key...");
            Console.ReadKey();
        }
    }
}

Result should be something like: