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

problem ：

I know that value types should be immutable, but that's just a suggestion, not a rule, right? I know that the value type should be immutable , But this is just a suggestion , Not the rules , Right ？So why can't I do something like this: Then why can't I do such a thing ：

struct MyStruct{    public string Name { get; set; }} public class Program{    static void Main(string[] args)    {        MyStruct[] array = new MyStruct[] { new MyStruct { Name = "1" }, new MyStruct { Name = "2" } };        foreach (var item in array)        {            item.Name = "3";        }        //for (int i = 0; i < array.Length; i++)        //{        //    array[i].Name = "3";        //}        Console.ReadLine();    }}

The foreach loop in the code doesn't compile while the commented for loop works fine. In code foreach Loop cannot compile , And annotated for The cycle works normally .The error message: error message ：

Cannot modify members of 'item' because it is a 'foreach iteration variable' Can't modify “item” Members of , Because it is “foreach Iterative variable ”

Why is that? Why is that ？

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Solution ：

Reference resources ： https://stackoom.com/en/question/Ni0P