What is a read only collection?

I ran a security code analyst i found myself having a CA2105 warning. I looked at the grade tampering example. I didn't realize you can assign int[] to a readonly int. I thought readonly was like the C++ const and makes it illegal.

The How to Fix Violations suggest i clone the object (which i don't want to do) or 'Replace the array with a strongly typed collection that cannot be changed'. I clicked the link and see 'ArrayList' and adding each element one by one and it doesn't look like you can prevent something adding more.

So when i have this piece of code what is the easiest or best way to make it a read only collection开发者_如何学编程?

public static readonly string[] example = { "a", "b", "sfsdg", "sdgfhf", "erfdgf", "last one"};

The easiest way to have a collection which you cannot modify is to use

ReadOnlyCollection

Example from MSDN:

List<string> dinosaurs = new List<string>();
dinosaurs.Add("Tyrannosaurus");
dinosaurs.Add("Amargasaurus");
dinosaurs.Add("Deinonychus");
dinosaurs.Add("Compsognathus");

ReadOnlyCollection<string> readOnlyDinosaurs = new ReadOnlyCollection<string>(dinosaurs);

public static readonly ReadOnlyCollection<string> example
    = new ReadOnlyCollection<string>(new string[] { "your", "options", "here" });

(although it should still probably be exposed as a get property rather than a public field)

If you're working with arrays, you can use

return Array.AsReadOnly(example);

to wrap your array in a read-only collection.

var readOnly = new ReadOnlyCollection<string>(example);

ReadOnlyCollection<string> readOnlyCollection = 
            new ReadOnlyCollection<string>(example);

I was looking for a similar solution, but I wanted to still be able to modify the collection from inside the class so I chose the option outlined here: http://www.csharp-examples.net/readonly-collection/

In short, his example is:

public class MyClass
{
    private List<int> _items = new List<int>();

    public IList<int> Items
    {
        get { return _items.AsReadOnly(); }
    }
}