Question: I am compulsive and like visually clean designs.

Theres a pop up in my app that tells the user that there's an error. 

I made a clear button over the entire pop up (about 200x100 px) so the user can just touch the notification to dismiss it.

But i'm afraid the user might not know that you can just touch the pop up to dissmiss and would go crazy looking for the "OKAY" button. 

Do you guys think the OKAY button is necessary or is a giant clear button overlaying the notification good enough? 

note: the whole notification actually looks like a button because of rounded corners and some button like borders.

Answer: 
`Where` returns a new sequence of items matching the predicate.

`Any` returns a Boolean value; there's a version with a predicate (in which case it returns whether or not any items match) and a version without (in which case it returns whether the query-so-far contains any items).

I'm not sure about `Exists` - it's not a LINQ standard query operator. If there's a version for the Entity Framework, perhaps it checks for existence based on a key - a sort of specialized form of `Any`? (There's an `Exists` method in `List<T>` which is similar to `Any(predicate)` but that predates LINQ.)
Just so you can find it next time, here is how you search for the enumerable Linq extensions. The methods are static methods of Enumerable, thus Enumerable.Any, Enumerable.Where and Enumerable.Exists.

* [google.com/search?q=Enumerable.Any](http://www.google.com/search?q=Enumerable.Any)
* [google.com/search?q=Enumerable.Where](http://www.google.com/search?q=Enumerable.Where)
* [google.com/search?q=Enumerable.Exists](http://www.google.com/search?q=Enumerable.Exists)

As the third returns no usable result, I found that you meant List.Exists, thus:

* [google.com/search?q=List.Exists](http://www.google.com/search?q=List.Exists)

I also recommend [hookedonlinq.com](http://www.hookedonlinq.com/) as this is has very comprehensive and clear guides, as well clear explanations of the behavior of Linq methods in relation to deferness and lazyness.