using System;
using System.Linq;
namespace pc.linq06
{
class Program
{
static void Main(string[] args)
{
var nums = Enumerable.Range(0, 20);
var groups1 = from n in nums
group n by (n % 2 == 0 ? "Even" : "Odd");
var groups2 = nums.GroupBy(n => n % 2 == 0 ? "Even" : "Odd");
foreach (var group in groups1) {
Console.Write($"\n{group.Key}\t" );
Array.ForEach(group.ToArray(), n => Console.Write(n + ", "));
}
Console.WriteLine();
foreach (var group in groups2) {
Console.Write($"\n{group.Key}\t");
Array.ForEach(group.ToArray(), n => Console.Write(n + ", "));
}
Console.WriteLine();
}
}
}
When using the group by functionality our result is a collection of groups, now the above is a simple example where we use a func<int,string> for our grouping function, this is to give our groupings a friendly name.
if we use a more complex object in our collection we can just leverage that objects property values for our group key, so below we'll create two groups one for last names one for first names.
using System;
using System.Linq;
namespace pc.linq07
{
class Person
{
public string
FirstName { get; set; }
public string LastName
{ get; set; }
public Person(string
FirstName, string LastName)
{
this.FirstName = FirstName;
this.LastName = LastName;
}
}
class Program
{
static void Main(string[] args)
{
var ppl = new Person[] { new Person("Pawel", "Chooch"),
new Person("Magda", "Tyvoniuk"), new Person("Jake", "Smith"),
new Person("Adam", "Chooch"), new Person("Pawel","Smith"),
new Person("Tomek", "Chooch"), new Person("Adam","Smith"),
new Person("Jake","Tyvoniuk")};
var LastNames = from p in ppl
group p by p.LastName;
var FirstNames = ppl.GroupBy(p => p.FirstName);
Console.WriteLine("Last Names:");
foreach (var lngroup in LastNames) {
Console.WriteLine(lngroup.Key);
Array.ForEach(lngroup.ToArray(), p => Console.WriteLine($"\t{p.FirstName}"));
}
Console.WriteLine("\nFirst Names:");
foreach (var lngroup in FirstNames) {
Console.WriteLine(lngroup.Key);
Array.ForEach(lngroup.ToArray(), p => Console.WriteLine($"\t{p.LastName}"));
}
}
}
}
using System;
using System.Linq;
namespace pc.linq07
{
class Person
{
public string
FirstName { get; set; }
public string LastName { get; set; }
public Person(string
FirstName, string LastName)
{
this.FirstName = FirstName;
this.LastName = LastName;
}
}
class Program
{
static void Main(string[] args)
{
var ppl = new Person[] { new Person("Pawel", "Chooch"),
new Person("Magda", "Tyvoniuk"), new Person("Jake", "Smith"),
new Person("Adam", "Chooch"), new Person("Pawel","Smith"),
new Person("Tomek", "Chooch"), new Person("Adam","Smith"),
new Person("Jake","Tyvoniuk")};
var LastNameLengths = from p in ppl
group p by GetStringLengthValue(p.LastName.Length);
var FirstNameLengths =
ppl.GroupBy(p =>
GetStringLengthValue(p.FirstName.Length));
Console.WriteLine("Last Name lengths:");
foreach (var lngroup in LastNameLengths) {
Console.WriteLine(lngroup.Key);
Array.ForEach(lngroup.ToArray(), p => Console.WriteLine($"\t{p.LastName}"));
}
Console.WriteLine("\nFirst Name lengths:");
foreach (var lngroup in FirstNameLengths) {
Console.WriteLine(lngroup.Key);
Array.ForEach(lngroup.ToArray(), p => Console.WriteLine($"\t{p.FirstName}"));
}
}
static string
GetStringLengthValue(int length) {
switch (length) {
case 1:
return "One";
case 2:
return "Two";
case 3:
return "Three";
case 4:
return "Four";
case 5:
return "Five";
case 6:
return "Six";
case 7:
return "Seven";
case 8:
return "Eight";
default:
return "More
than Eight";
}
}
}
}
