System.Security.Util.TokenBasedSet.GetItem C# (CSharp) Method

        internal Object GetItem(int index)
        {
            switch (m_cElt)
            {
            case 0:
                return null;

            case 1:
                if (index == m_maxIndex)
                    return m_Obj;
                else
                    return null;
            default:
                if (index < m_Set.Length)
                    return m_Set[index];
                else
                    return null;
            }
        }

        // Used to merge two distinct TokenBasedSets (used currently only in PermissionSet Deserialization)
        internal TokenBasedSet SpecialUnion(TokenBasedSet other)
        {
            // This gets called from PermissionSet.OnDeserialized and it's possible that the TokenBasedSets have
            // not been subjected to VTS callbacks yet
            OnDeserializedInternal();
            TokenBasedSet unionSet = new TokenBasedSet();
            int           maxMax;

            if (other != null)
            {
                other.OnDeserializedInternal();
                maxMax = this.GetMaxUsedIndex() > other.GetMaxUsedIndex() ? this.GetMaxUsedIndex() : other.GetMaxUsedIndex();
            }
            else
            {
                maxMax = this.GetMaxUsedIndex();
            }

            for (int i = 0; i <= maxMax; ++i)
            {
                Object      thisObj  = this.GetItem(i);
                IPermission thisPerm = thisObj as IPermission;

                Object      otherObj  = (other != null)?other.GetItem(i):null;
                IPermission otherPerm = otherObj as IPermission;

                if (thisObj == null && otherObj == null)
                {
                    continue;
                }

                if (thisObj == null)
                {
                    PermissionToken token = PermissionToken.GetToken(otherPerm);

                    if (token == null)
                    {
                        throw new SerializationException(Environment.GetResourceString("Serialization_InsufficientState"));
                    }

                    unionSet.SetItem(token.m_index, otherPerm);
                }
                else if (otherObj == null)
                {
                    PermissionToken token = PermissionToken.GetToken(thisPerm);
                    if (token == null)
                    {
                        throw new SerializationException(Environment.GetResourceString("Serialization_InsufficientState"));
                    }
                    unionSet.SetItem(token.m_index, thisPerm);
                }
                else
                {
                    Debug.Assert((thisObj == null || otherObj == null), "Permission cannot be in both TokenBasedSets");
                }
            }
            return(unionSet);
        }