Func Delegates in LINQ
//public delegate TR Func<TR>();
//public delegate TR Func<T0, TR>(T0 a0);
//public delegate TR Func<T0, T1, TR>(T0 a0, T1 a1);
//public delegate TR Func<T0, T1, T2, TR>(T0 a0, T1 a1, T2 a2);
//public delegate TR Func<T0, T1, T2, T3, TR>(T0 a0, T1 a1, T2 a2, T3 a3);
// simply define a int[]
int[] ints = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
// Declare our delegates on top of defined delegates.
Func<int, int> MultiplyWithThree = i => i * 3;
Func<int, bool> GreaterThanTwo = i => i > 2;
Func<int, int, int> MultiplyTwo = (i,j) => i * j;
Func<double, double, double> MultiplyTwoDoubles = (i, j) => i * j;
Func<double, double, double, double> MultiplythreeDoubles = (i, j, k) => i * j * k;
Func<double, double, double, double, double> MultiplyFourDoubles = (i, j, k, L) => i * j * k * L;
//Use them
IEnumerable<int> intsMultipliedByThree = ints.Select(MultiplyWithThree);
IEnumerable<int> intsGreaterThanTwo = ints.Where(GreaterThanTwo);
IEnumerable<int> intsMultiplied =
from i in ints
from j in ints where i ==j
select (MultiplyTwo(i, j));
IEnumerable<double> doublessMultiplied =
from i in ints
from j in ints
where i == j
select (MultiplyTwoDoubles((double)i, (double)j));
IEnumerable<double> intsThreeMultiplied =
from i in ints
from j in ints
from k in ints
where i == j && j == k
select (MultiplythreeDoubles(i, j, k));
IEnumerable<double> intsFourMultiplied =
from i in ints
from j in ints
from k in ints
from l in ints
where i == j && j == k
select (MultiplyFourDoubles(i, j, k,l));