In C#, why can't I modify the member of a value type instance in a foreach loop?

Question

I know that value types should be immutable, but that\'s just a suggestion, not a rule, right? So why can\'t I do something like this:

struct MyStruct
{
             


        

Answer 1

It's a suggestion in the sense that there's nothing stopping you from violating it, but it should really be afforded much more weight than "it's a suggestion". For instance, for the reasons you're seeing here.

Value types store the actual value in a variable, not a reference. That means that you have the value in your array, and you have a copy of that value in item, not a reference. If you were allowed to change the values in item, it would not be reflected on the value in the array since it's a completely new value. This is why it isn't allowed.

If you want to do this, you'll have to loop over the array by index and not use a temporary variable.