Question

I have a class that extends SortedList. I can use the many of the SortedList methods in my class like Add() and Remove() but for some reason it doesn’t like it when I try to use GetKey(). Can anyone tell me why this might be happening?

public class SymbolTableImplementation : SortedList<string, SymbolTableEntry>, SymbolTable
{
    public SymbolTableEntry Enter(string name)
    {
        SymbolTableEntry entry = SymbolTableFactory.CreateSymbolTableEntry(name, this);
        Add(name, entry);  // This is OK
        return entry;
    }

    //  Look up an existing symbol table entry. Null if it does not exist.
    public SymbolTableEntry Lookup(string name)
    {
        return GetKey(name);  // Doesn't exist in current context
    }
}

Answer 1

GetKey is defined in SortedList, which is actually a completely separate class from SortedList<TKey, TValue>. You also have a mistake in your original code; if you were actually using GetKey/SortedList, this would not have compiled:

return GetKey(name);

Instead, just use the IDictionary indexer:

return this[name];