Confusion on TUTORIALS IN MVC1

.NET
1

I have an e-book THE MVC1 Quickly…
There is a part there


public ActionResult UpdateContact()
{
int id = 0;
if (int.TryParse(Request.Form["Id"], out id))
{
Contact contact = Contacts.Single(c => c.Id == id);
contact.Name = Request.Form["Name"];
contact.Email = Request.Form["Email"];
}
return RedirectToAction("Index");
}

What does c for? Its not even declared?

2

It’s Linq. .Single chooses one record from the collection and throws an exception if more than one record exists to meet the select. c is defined in the delegate. It selects the record where the collection’s Id is equal to id from the form.

3

Delegates are confusing to those new to them. So let me step it out…

The line “Contacts.Single(c => c.Id == id)” should simple be read like this:

From Contacts I want a Single contact, which we shall call c, where c.Id is equivalent to id.

c is merely a placeholder. The (c => ?) part just says, look at each element in the set and if it meets condition ? then return it. Personally, I don’t like using single letters like that. The following is more clear.

var desiredContact = Contacts.Single(contact => contact.Username == “foobar”);
// grab the one contact from the set where username is foobar.

Note: if record does not exist, the Single method will throw an exception. If you don’t want to handle them, use SingleOrDefault instead.