根据Parameter类型来取值

string GetParameterVal(Document doc,Parameter para)
        {
            string strVal = "";

　　　　switch (para.StorageType)
            {
                case StorageType.Double:
                    break;
                case StorageType.ElementId:
                    break;
                case StorageType.Integer:
                    break;
                case StorageType.None:
                    break;
                case StorageType.String:
                    break;
                default:
                    break;
            }
            return strVal;
        }