public static void Demo2()
{
Employee[] employees = Employee.GetEmployeesArray();
EmployeeOptionEntry[] empOptions = EmployeeOptionEntry.GetEmployeeOptionEntries();
var employeeOptions = employees
.SelectMany(e => empOptions
.Where(eo => eo.id == e.id)
.Select(eo => new
{
id = eo.id,
optionsCount = eo.optionsCount
}));
foreach (var item in employeeOptions)
{
Console.WriteLine(item);
}
/*
* { id = 1, optionsCount = 2 }
* { id = 2, optionsCount = 10000 }
* { id = 2, optionsCount = 10000 }
* { id = 2, optionsCount = 10000 }
* { id = 3, optionsCount = 5000 }
* { id = 3, optionsCount = 7500 }
* { id = 3, optionsCount = 7500 }
* { id = 4, optionsCount = 1500 }
* { id = 101, optionsCount = 2 }
*/
}
public static void EmployeeOptions()
{
EmployeeOptionEntry[] EmpOptions = EmployeeOptionEntry.GetEmployeeOptionEntries();
var Employees = Initial_Get_Employee_Array_List.shared_Employee_Classes;
var employeeOptions = Employees
.SelectMany(e => EmpOptions
.Where(eo => eo.id == e.id)
.Select(eo => new
{
Id = eo.id,
OptionsCount = eo.optionsCount
}));
foreach (var items in employeeOptions)
{
Console.WriteLine(items);//OutPut: { id = 1, optionsCount = 2 } ... id = 101
}
//======================================Sumary====================================
//This looks like a lot but lets step through it. In the example every employee in the
//Employee list is passed into he lambda expression which is then passed into the
//selectmany Operator. The lambda expression will then get every entry of employee
//optionEntry elements whos ID matches the ID of the current employee passed into it
//After that the lambda creates a new anonymous object for each matching ID
//TLDR: Takes every matching id from the two arrays and adds them into their own object.
//================================================================================
}
public static EmployeeOptionEntry[] GetEmployeeOptionEntries()
{
EmployeeOptionEntry[] empOptions = new EmployeeOptionEntry[] {
new EmployeeOptionEntry {
id = 1,
optionsCount = 2,
dateAwarded = DateTime.Parse("1999/12/31")
},
new EmployeeOptionEntry {
id = 2,
optionsCount = 10000,
dateAwarded = DateTime.Parse("1992/06/30")
},
new EmployeeOptionEntry {
id = 2,
optionsCount = 10000,
dateAwarded = DateTime.Parse("1994/01/01")
},
new EmployeeOptionEntry {
id = 3,
optionsCount = 5000,
dateAwarded = DateTime.Parse("1997/09/30")
},
new EmployeeOptionEntry {
id = 2,
optionsCount = 10000,
dateAwarded = DateTime.Parse("2003/04/01")
},
new EmployeeOptionEntry {
id = 3,
optionsCount = 7500,
dateAwarded = DateTime.Parse("1998/09/30")
},
new EmployeeOptionEntry {
id = 3,
optionsCount = 7500,
dateAwarded = DateTime.Parse("1998/09/30")
},
new EmployeeOptionEntry {
id = 4,
optionsCount = 1500,
dateAwarded = DateTime.Parse("1997/12/31")
},
new EmployeeOptionEntry {
id = 101,
optionsCount = 2,
dateAwarded = DateTime.Parse("1998/12/31")
}
};
return(empOptions);
}
//====================================Join====================================
//The join operator performs an inner equiijoin on 2 sequences, comparing the
//extracted keys from the elements.
//===================================Prototype================================
//
// public static IEnumerable<V> Join<T, U, K, V>(
// this IEnumerable<T> outer,
// IEnumerable<U> inner,
// Func<T, K> outerKeySelector,
// Func<U, K> innerKeySelector,
// Func<T, U, V> resultSelector);
//
//===================================Sumary===================================
//The first method is called outer. Since this is an extension method, the obj
//we are calling this on will be considered the outer. The operator will return
//an object when enumerated will first enumerate the inner sequence(U). This calls
//the inner keyselector once for each element in the sequence. This stores the
//elements referenced with a specific key into a hash table. After the same thing
// will occur for the outer sequence(T). for each matching inner and outer element
//pair the resultSelector method (v) will be called.
//=============================================================================
public static void JoinEmployees()
{
var joinByIds = Initial_Get_Employee_Array_List.shared_Employee_Classes
.Join(
EmployeeOptionEntry.GetEmployeeOptionEntries(), //Inner Sequence
e => e.id, //outer KeySelector
i => i.id, //Inner KeySelector
(e, i) => new //Result Selector
{
id = e.id,
name = string.Format($"{e.firstName} {e.lastName}"),
options = i.optionsCount
});
foreach (var item in joinByIds)
{
Console.WriteLine(item);
}
}
