static void Main(string[] args)
{
// The Where Operator
// var record = DataLoader.Load(@"./");
// var femaleTop10 = record
// .Where(r => r.Gender == Gender.Female && r.Rank <= 10);
// var maleTop10 = from r in record
// where r.Gender == Gender.Male && r.Rank <= 10
// select r;
// foreach (var r in femaleTop10)
// System.Console.WriteLine(r);
// foreach (var r in maleTop10)
// System.Console.WriteLine(r);
//----------------------------------------------------------------------------
// The OfType Operator
// var objects = new Object[] { 1, 10L, 1.1, 1.1f, "Hello", 2, 3 };
// var result = objects.OfType<int>();
// foreach (var item in result)
// {
// System.Console.WriteLine(item);
// }
//----------------------------------------------------------------------------
// The All Operator
// The All operator determines whether all the elements in a collection satisfy a condition.
// All operators does not have query expression (SQL-like) syntax.
// var records = DataLoader.Load(@"./");
// var result = records.All(r => r.Name.Length > 3);
// System.Console.WriteLine(result);
//----------------------------------------------------------------------------
// The Any Operator
// Any operator determines whether there is at least one element
// in the source collection that satisfies the condition.
// Any operators does not have query expression (SQL-like) syntax.
// var records = DataLoader.Load(@"./");
// var result = records.Any(r => r.Name.Length > 15);
// System.Console.WriteLine(result);
//----------------------------------------------------------------------------
// The Contains Operator
// The Contains operator determines whether a collection contains a specified element.
// Any operators does not have query expression (SQL-like) syntax.
// int[] integers = { 100, 200, 300, 400, 500 };
// string[] strings = { "Tim", "Tom", "Rina", "Andrew" };
// var result1 = integers.Contains(200);
// var result2 = strings.Contains("Tim");
// System.Console.WriteLine($"{result1} {result2}");
//----------------------------------------------------------------------------
// The Set Operators
// Distinct - Keeps unique elements of the collection and removes duplicate elements
// Intersect - Returns the set intersection, which means elements that appear in each of two collections
// Except - Returns the set difference, which means the elements of one collection that do not appear in a second collection
// Union - Returns the set union, which means unique elements that appear in either of two collections
// All these four operators do not have query expression(SQL - like) keywords.
// int[] left = { 1, 1, 2, 3, 3, 4, 4 };
// int[] right = { 3, 4, 5, 6 };
// var distinctResult = left.Distinct();
// var intersectResult = left.Intersect(right);
// var exceptResult = left.Except(right);
// var unionResult = left.Union(right);
// Console.WriteLine($"Distinct: {string.Join(",", distinctResult)}"); // 1, 2, 3, 4
// Console.WriteLine($"Intersect: {string.Join(",", intersectResult)}"); // 3, 4
// Console.WriteLine($"Except: {string.Join(",", exceptResult)}"); // 1, 2
// Console.WriteLine($"Union: {string.Join(",", unionResult)}"); // 1, 2, 3, 4, 5, 6
//----------------------------------------------------------------------------
// The Concat Operator
// Concatenation refers to the operation of appending one collection to another
// int[] array1 = { 1, 2, 3, 4, 5 };
// int[] array2 = { 3, 4, 5, 6, 7 };
// var concatResult = array1.Concat(array2); // 1,2,3,4,5,3,4,5,6,7
// var unionResult = array1.Union(array2); // 1,2,3,4,5,6,7
// System.Console.WriteLine($"Concat: {string.Join(",", concatResult)}");
// System.Console.WriteLine($"Union: {string.Join(",", unionResult)}");
//----------------------------------------------------------------------------
// The OrderBy Operator
// Sorts values in ascending order
// var records = DataLoader.Load(@"./");
// var sortedByRank = records.OrderBy(r => r.Rank);
// // The corresponding query expression (SQL-like) syntax
// // var sortedByRank = from r in records orderby r.Rank select r;
// foreach (var r in sortedByRank)
// {
// System.Console.WriteLine(r.ToString());
// }
//----------------------------------------------------------------------------
// The OrderByDescending Operator
// Sorts values in descending order
// var records = DataLoader.Load(@"./");
// var sortedByRank = records.OrderByDescending(r => r.Rank);
// // The corresponding query expression (SQL-like) syntax
// // var sortedByRank = from r in records orderby r.Rank descending select r;
// foreach (var r in sortedByRank)
// {
// System.Console.WriteLine(r.ToString());
// }
/*
* Note:
* Some of the .NET built-in collections has their own Sort and Reverse member methods.
* The difference between the member methods and the LINQ methods is the member methods
* will perform the sorting on the collection, thus the element sequence of the collection
* will be physically changed. While the LINQ method will generate a new result collection
* which is sorted, the source collection keeps its original element sequence.
*/
//----------------------------------------------------------------------------
// The ThenBy Operator
// Performs a secondary sort in ascending order.
// var records = DataLoader.Load(@"./");
// var sortedByRank = records.OrderBy(r => r.Rank).ThenBy(r => r.Name);
// // The corresponding query expression (SQL-like) syntax
// // var sortedByRank = from r in records orderby r.Rank, r.Name select r;
// foreach (var r in sortedByRank)
// {
// System.Console.WriteLine(r.ToString());
// }
//----------------------------------------------------------------------------
// The ThenByDescending operator
// Performs a secondary sort in descending order
// var records = DataLoader.Load(@"./");
// var sortedByRank = records.OrderBy(r => r.Rank).ThenByDescending(r => r.Name);
// // The corresponding query expression (SQL-like) syntax
// // var sortedByRank = from r in records orderby r.Rank, r.Name descending select r;
// foreach (var r in sortedByRank)
// {
// System.Console.WriteLine(r.ToString());
// }
//----------------------------------------------------------------------------
// The Reverse Operator
// Reverses the order of the elements in a collection
// int[] original = { 1979, 10, 31, 8, 15 };
// var reversed = original.Reverse();
// System.Console.WriteLine($"Original: {string.Join(",", original)}");
// System.Console.WriteLine($"Reversed: {string.Join(",", reversed)}");
//----------------------------------------------------------------------------
// The Select Operator
// Projects values that are based on a transform function.
// var records = DataLoader.Load(@"./");
// // var names = records.Select(r => r.Name);
// // Using the query expression (SQL-like) syntax, the code will be:
// // var names = from r in records select r.Name;
// // Select Multiple Element Property Values
// var items = records.Select(r => new { Rank = r.Rank, Name = r.Name });
// // Using the query expression (SQL-like) syntax, the code will be:
// // var items = from r in records select new { Rank = r.Rank, Name = r.Name };
// foreach (var n in items)
// {
// System.Console.WriteLine(n);
// }
// When using ValueTuple, the code will be:
// var records = DataLoader.Load(@"./");
// var items = records.Select(r => (r.Rank, r.Name));
// // query expression (SQL-like) syntax version of this code is:
// // var items = from r in records select (r.Rank, r.Name);
// foreach (var item in items)
// {
// // System.Console.WriteLine(item.GetType());
// System.Console.WriteLine($"Rank:{item.Rank} Name:{item.Name}");
// }
//----------------------------------------------------------------------------
// The SelectMany Operator
// Projects sequences of values that are based on a transform function and then flattens them into one sequence.
// Prepare the data
var records = DataLoader.Load(@"./");
var dict = new Dictionary <string, IEnumerable <Record> >();
dict["FemaleTop5"] = records.Where(r => r.Rank <= 5 && r.Gender == Gender.Female);
dict["MaleTop5"] = records.Where(r => r.Rank <= 5 && r.Gender == Gender.Male);
// Solution 1:
var names1 = new List <string>();
var selectResult = dict.Select(kvp => kvp.Value);
foreach (var c in selectResult)
{
foreach (var r in c)
{
names1.Add(r.Name);
}
}
// Solution 2:
var names2 = new List <string>();
var selectManyResult = dict.SelectMany(kvp => kvp.Value);
foreach (var r in selectManyResult)
{
names2.Add(r.Name);
}
// Solution 3:
var names3 =
from kvp in dict
from r in kvp.Value
select r.Name;
}