CODEWITHSUNDEEP
c#arrays
user4520
user4520

Reputation: 3459

is there any possibility to alter an array element by modifying its copy?

I'm working on quite a complex project and have been struggling to debug one problem for the last hour. I nailed down the troublesome code which looks more or less like this:

Client ClientToChange = Clients[index];
ClientToChange.Rank = 80;

Clients is a static array of classes Client, declared in the same class.

Changing ClientToChange's rank for some reason alters the contents of the array, i.e.

Console.WriteLine(Clients[index].Rank)

returns 80 (whereas before it was 100), of course index was not changed.

This seems bizarre to me, but that's what happens.

I wrote a little dummy program to test this out, just to make sure:

    static string[] foo = new string[10];
    static void Main(string[] args)
    {

        foo[3] = "bar";

        string test = "";
        test = foo[3];

        test = "fb";

        Console.Write(foo[3]);
        Console.Write(test);

This, of course, works like it should: prints barfb.

Am I doing something that I cannot see, or I don't know something I should?

Upvotes: 2

Views: 78

Answers (1)

Gareth Latty
Gareth Latty

Reputation: 88977

When you do the assignment

Client ClientToChange = Clients[index];

You are making ClientToChange a reference to the object at Clients[index], not copying it. They are both names that happen to point to the same object. It makes sense that when you change it, you see those changes, whichever name you use (a reference in an array is just a particular type of name).

If you want a different object, you should copy it.

The reason your string case doesn't show this behaviour is because in that case, you are not modifying the contained string, but rather changing the name to point to another object. Changing what one name points to doesn't change what the other names point to. If you were to mutate the string (which you can't do, as C# strings are immutable), then you would see the change when accessing it through the array.

Upvotes: 5

Related Questions