Click on this link to open an Office Mix that provides a good introduction on how to customize model elements.
This model is compiled into its own separate assembly.In Microsoft Dynamics AX 2012, you could override form methods.In the current version, you use extensions to implement event handlers that are called from the base implementations of form methods.Extension models have several advantages, including: Events are raised as preceding and succeeding operations around the base methods.This means that you have the opportunity to run code before a base method is called and after it has completed.For example, solution developers can provide code in the SLN layer, independent software vendors can use the ISV layer, and value-added resellers can use the VAR layer.
Functionality defined in higher layers (VAR layer in this example) can override the functionality of lower layers.
Using table extensions, you can also change the Extended Data Type property on fields and set it to an EDT that is derived from the current EDT ().
In Microsoft Dynamics AX 2012, you could override the virtual methods of a table's base class to control the behavior that occurred during table operations, such as when creating, reading, updating, or deleting.
Filtered Text Box 功能：文本框数据过滤 细节： (1)过滤条件Numbers Lowercase Letters Uppercase Letters Custom (2)过滤条件也可以是Custom的组合 Filter Type="Custom, Numbers" (3)Valid Chars=" -=/*()." Custom要定义这样的有效字符串 (4) 其实这是个鸡肋：你可以输入中文，聊胜于无，忍了12.
Hover Menu 功能：鼠标靠近时显示菜单，可以用在在线数据修改的表格上作为功能菜单 细节： (1)Popup Control ID要弹出来什么 (2)Popup Postion 在哪里弹出来Left (Default), Right, Top, Bottom, Center. Popup Control 功能：任何控件上都可以弹出任何内容 细节： (1)Target Control ID - The ID of the control to attach to (2)Popup Control ID - The ID of the control to display (3)Commit Property -属性来标识返回的值 (4) Commit Script -把返回结果值通过脚本处理，用到Commit Property21.
Cascading Drop Down 功能：Drop Down List联动，调用Web Service 细节： (1)Drop Down List行为扩展 (2)如果使用Web service 方法签名必须符合下面的形式： [Web Method] public Cascading Drop Down Name Value Get Drop Down Contents( string known Category Values, string category)10.