Lambda Expressions in C#
Lambda Expressions are very powerful when it comes to filtering sets. There are built in methods such as Where() or FindAll() available for most collections in C#. These methods use Lambda Expressions for filtering. I have listed a few examples below.
Find evens in a list of positive integers
List numbers = Enumerable.Range(1, 100).ToList();
var evens = numbers.FindAll(n => n % 2 == 0);
Find primes in a list of positive integers
List numbers = Enumerable.Range(1, 100).ToList();
for (int i = 2; i < 8; i++) {
numbers = numbers.Where( n => (n > 1) && ( (n == i) || (n % i > 0) ) ).ToList();
}
Although, it is probably not necessary to explain the expression above; prime numbers cannot be devided by 2, 3, 5, 7 and not equal to 1. Why doesn’t it matter that 4 and 6 are in the loop too? It is because 4 is a multiple of 2 and 6 is a multiple of 3. If a number is devisible by the multiple of a prime number then it must be devisible by the base prime too. Therefore anything that is devisible by 4 or 6 cannot be a prime.
Lambda Expressions can use Generic Delegates to ensure that the input, output is matching a given type. For instance, the expression below will return a compiler error because the inferred type is a double.
Func<double,double> giveMeDouble = (x) => x / 2;
int MyInt = giveMeDouble(1);
This short introduction is not even scratching the surface of what Expressions can do. If you want more information about Expressions check out ExpressionTrees on MSDN.
 | Beginning Programming For Dummies New techniques make programming easier and more fun Discover principles and best practices that let you program in many languages So you always thought programmers were superior beings from another galaxy? Surprise!… |
