about linq, IEnumerable<T> and Lambda expression

[Tony Johansson]

Hello!

I have this linq query below with two lambda expressions.

If I look at the documentation for Where operator it says.
public static IEnumerable<T> Where<T>(
this IEnumerable<T> source,
Func<T, bool> predicate);

In my case where I have a Where operator it will match the second row that
says
Func<T, bool> predicate
In my where operator, T is an int and I return bool.

Now to my question what does it mean with the first row that says
* this IEnumerable<T> source *
and what can it be used for ?


int[] nums = new int[] {6,2,7,1,9,3};
IEnumerable<int> numsLessThenFour = nums
..Where(i => i<4)
..OrderBy(i => i);

foreach(int number in numsLessThenFour )
Console.WriteLine(number);

//Tony

 

[Peter Morris]

Now to my question what does it mean with the first row that says

* this IEnumerable<T> source *

IEnumerable<T> source

This is the source, in your case "nums"

But, instead of you having to write

SomeStaticClassName.Where(nums, someFunc)

the "this" statement makes "Where" an extension method on anything that
implements IEnumerable<T> (which an array of byte does), so you can instead
write

nums.Where(someFunc)

which is the same as

Where(nums, someFunc)

 

[Martin Honnen]

If I look at the documentation for Where operator it says.
public static IEnumerable<T> Where<T>(
this IEnumerable<T> source,
Func<T, bool> predicate);

Now to my question what does it mean with the first row that says
* this IEnumerable<T> source *
and what can it be used for ?

public static IEnumerable<T> Where<T>(
this IEnumerable<T> source,
means the Where method (as other LINQ methods) is implemented as an
extension method.

If you look at the methods of the IEnumerable<T> interface
http://msdn.microsoft.com/en-us/library/ckzcawb8.aspx
then you will see that only GetEnumerator is implemented as a "normal"
methods while all the LINQ query methods are implemented as extension
methods. With C# and VB.NET you can call extension methods like normal
instance methods.