C# foreach on IEnumerable vs. List - element modification persistent only for array - Why?

Question

In C#, I have noticed that if I am running a foreach loop on a LINQ generated IEnumerable collection and try to modify the contents of each T element,

Answer 1

You are right, it is deferred execution. A new MyClass instance is created each time you iterate the IEnumerable. By calling ToList or ToArray you then create a List or Array and populate it with the new MyClass instances created from the iteration of the IEnumerable.