readonly keyword does not make a List<> ReadOnly?

Question

I have the following code in a public static class:

public static class MyList
{
    public static readonly SortedList> CharList         


        

Answer 1

The readonly modifier just gaurantees that the variable 'CharList' cannot be re-assigned to something else from outside of the class constructor. You need to create your own dictionary structure that doesn't have a public Add() method.

class ImmutableSortedList 
{
    SortedList mSortedList;

    public ImmutableSortedList(SortedList sortedList) // can only add here (immutable)
    {
        this.mSortedList = sortedList; 
    }

    public implicit operator ImmutableSortedList(SortedList sortedList)
    {
        return new ImmutableSortedList(sortedList); 
    }
}

Or, if you truly can't change the implementation, make the SortedList private and add your own methods that control access to it:

class MyList
{
    // private now
    readonly SortedList> CharList;

    // public indexer
    public List this[int index]
    {
        get { return this.CharList[index]; }
    }
}