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.)
Any - boolean function that returns true when any of object in list satisfies condition set in function parameters. For example:

```
List<string> strings = LoadList();
boolean hasNonEmptyObject = strings.Any(s=>string.IsNullOrEmpty(s));

```

Where - function that returns list with all objects in list that satisfy condition set in function parameters. For example:

```
IEnumerable<string> nonEmptyStrings = strings.Where(s=> !string.IsNullOrEmpty(s));

```

Exists - basically the same as any but it's not generic - it's defined in List class, while Any is defined on IEnumerable interface.