Question

I am trying to fix the size of the Hashtable with following code.

       Hashtable hashtable = new Hashtable(2);

        //Add elements in the Hashtable
        hashtable.Add("A", "Vijendra");
        hashtable.Add("B", "Singh");
        hashtable.Add("C", "Shakya");
        hashtable.Add("D", "Delhi");
        hashtable.Add("E", "Singh");
        hashtable.Add("F", "Shakya");
        hashtable.Add("G", "Delhi");
        hashtable.Add("H", "Singh");
        hashtable.Add("I", "Shakya");
        hashtable.Add("J", "Delhi");

I have fix the size of this Hashtable is 2 but I can add more than 2 elements in this, why this happen, I am doing somthing wrong?

I have tried to find out is this Hashtable have fix size of not with hashtable.IsFixedSize, it always returns false

Please tell me where I am wrong, or there is another way..

Answer 1

Once you’ve added all the elements you need, you need to implement a read-only version of IDictionary that you can then use to disallow altering existing entries (look at subclassing Hashtable, and overriding all the methods/properties which alter values to throw NotSupportedException). You can then override IsReadOnly and IsFixedSize to return whatever values you need.

I would also recommend you use the generic Dictionary<TKey, TValue> instead of Hashtable, as you get better compile-time safety and better performance with value types. However, you would have to create your own read-only implementation of IDictionary<TKey, TValue>, as none of the Dictionary methods are virtual.