Casting and Linq Cast<T>()

Question

When trying to answer this question, I discovered the following:

string s = "test";

var result1 = s.Select(c => (ushort)c); // works fine

var result2 = s.Cast<ushort>(); // throws an invalid cast exception

Why does Cast<T>() fail here? Whats the difference?

Answer 1

I believe using the Cast() extension method only takes default (non-user cast), implicit casts into account or casts from a more general type (e.g., object). Otherwise it fails.

Turns out this is the case.

Answer 2

Think you will find your answer here:

http://stackoverflow.com/questions/445471/puzzling-enumerable-cast-invalidcastexception

The last part, under Edit:

Cast<T>() is an extension method on IEnumerable rather than IEnumerable<T>. That means that by the time each value gets to the point where it's being cast, it has already been boxed back into a System.Object