X++ Code Optimzation

Following are the coding tips to improve your Axapta system's performance:
1. Smart Joins : Try to Use Joins instead of nested while loop 
wherever possible.
2. Select Statement : Mention the field names in the select statement 
instead of feteching entire row , this will reduce 
data amount to transfer from database.
e.g " Select Itemid from inventTable "

3. Display Methods : Make sure that generic display methods should be 
moved at table level and cached by 
using"Formdatasource.cacheAddmethod". 
4. Local caching : Use Variables for storing the constantly used 
caculated values in loop , by doing so you can 
reduce the calls to the database and different 
layers.
5. Monitor the Database Calls : For bulk records 
updation,deletion,insertion use 
RecordSet Based operator like 
update_recordset , delete_from and insert_recordset .
6. Aggregate Function: Use sum, avg, minof, maxof and count where 
applicable. Because this can utilize the database’s 
built-in function instead of calculating and analyse 
data in Axapta.

Source : http://learnax.blogspot.in/2010_01_01_archive.html