How does LINQ's “Where” method works?

Question

Exactly how LINQ\'s \"where\" method is defined? I\'m guessing implementation is something like this:

public static IEnumerable Where ( this partialPare         


        

Answer 1

The query syntax you mention for where basically creates a method and delegate, and calls the method syntax version with it. Whatever you call where with is turned into a single method and then called via a delegate on each element of the source sequence.

So possibly what you mean by the two checks being passed as a whole expression; that's what is happening...

where ( c.Col1 == c.Col2 || c.Col3 == c.Col4 )

it turned into a single method call like this:

bool MethodExample(var c){
  return ( c.Col1 == c.Col2 || c.Col3 == c.Col4 );
}

and is then called on each element. (obviously the above is pseudo-code)