//ELEMENTS MANAGEMENT
 public override void setElement(IComplexNumber element, int posRows, int posCols)
 {
     if (element == null)
     {	_internalMatrix[posRows,posCols] = null;	}
     else
     {
         if (element.IsZero())
         {	_internalMatrix[posRows,posCols] = null;	}
         else
         {	_internalMatrix[posRows,posCols] = element;	}
     }
 }
        public override void setElement(IComplexNumber element, int posRows, int posCols)
        {
            string key = generateKey(posRows,posCols);

            if (element == null)
            //{	_internalMatrix[key] = null;	}
            { _internalMatrix.Remove(key);		}
            else
            {
                if (element.IsZero())
                    //{	_internalMatrix[key] = null;	}
                { _internalMatrix.Remove(key);		}
                else
                { _internalMatrix[key] = element;	}
            }
        }