What is the best way to modify a list in a 'foreach' loop?

Question

A new feature in C# / .NET 4.0 is that you can change your enumerable in a foreach without getting the exception. See Paul Jackson\'s blog entry An Interest

Answer 1

You can't change the enumerable collection while it is being enumerated, so you will have to make your changes before or after enumerating.

The for loop is a nice alternative, but if your IEnumerable collection does not implement ICollection, it is not possible.

Either:

1) Copy collection first. Enumerate the copied collection and change the original collection during the enumeration. (@tvanfosson)

or

2) Keep a list of changes and commit them after the enumeration.