Using LINQ extension method syntax on a MatchCollection

Question

I have the following code:

MatchCollection matches = myRegEx.Matches(content);

bool result = (from Match m in matches
               where m.Groups["nam         


        

Answer 1

When you specify an explicit range variable type, the compiler inserts a call to Cast. So this:

bool result = (from Match m in matches
               where m.Groups["name"].Value.Length > 128
               select m).Any();

is exactly equivalent to:

bool result = matches.Cast()
                     .Where(m => m.Groups["name"].Value.Length > 128)
                     .Any();

which can also be written as:

bool result = matches.Cast()
                     .Any(m => m.Groups["name"].Value.Length > 128);

In this case the Cast call is required because MatchCollection only implements ICollection and IEnumerable, not IEnumerable. Almost all the LINQ to Objects extension methods are targeted at IEnumerable, with the notable exceptions of Cast and OfType, both of which are used to convert a "weakly" typed collection (such as MatchCollection) into a generic IEnumerable - which then allows for further LINQ operations.