Special Features of Web Dynpro ABAP Programming 
There are some differences between programming Web Dynpro ABAP components and standard ABAP programming.
You cannot use lists or screen and control technology in Web Dynpro ABAP programming. For example,
CALL / LEAVE TO SCREEN
LEAVE TO LIST-PROCESSING
WRITE / ULINE / HIDE
MESSAGE
The program flow cannot be changed in Web Dynpro ABAP programming. You cannot use statements to exit the current session or to start a new one. For example:
CALL / LEAVE TO TRANSACTION
SUBMIT
LEAVE PROGRAM
You cannot use certain system commands in Web Dynpro ABAP programming. For example:
EDITOR-CALL
SYNTAX-CHECK/GENERATE
It is not permitted to access database tables within controller methods.
Functional enhancements of Web Dynpro components, such as methods and event handlers are called by Web Dynpro Framework. This fills all parameters. There is therefore no need to query the parameter interface.
IS SUPPLIED
IS REQUESTED
The integration of type pools and program includes is not supported in Web Dynpro ABAP programming.
Access to controller attributes and calls from controller methods must always be made using the controller self-reference WD_THIS.
For information about other restrictions in Web Dynpro ABAP, see SAP Note 1098009 .