Dynamics 365 Finance & Operations 绕过CoC调用链限制拓展重写系统类的方法

声明：此方法虽然可以有效修改系统类，但是并不是微软推崇的方式，虽然有效，但有可能会影响系统类在将来的更新中的功能，请谨慎使用！

假如我们要修改系统工作流按钮的生成，我们可以这样操作：

代码

internal final class OverrideSysWorkflowFormControls extends SysWorkflowFormControls
{
    /// <summary>
    /// Event handler for consturct method in <c>SysWorkflowFormControls</c>.
    /// </summary>
    /// <param name = "args">Method args.</param>
    [Hookable(false), PostHandlerFor(classStr(SysWorkflowFormControls), staticMethodStr(SysWorkflowFormControls, construct))]
    public static void SysWorkflowFormControls_Post_construct(XppPrePostArgs args)
    {
        FormRun form = Args.getArg(literalStr(_form));

        if (form.name() == formStr(FormNeedsAOverride))
        {
            Args.setReturnValue(OverrideSysWorkflowFormControls::construct(form));
        }
    }

    //下面是复制的原始代码，可以在这里对逻辑进行修改，要带[Hookable(false)]
    [Hookable(false)]
    public void initControls()
    {
        #Resource
        #ResAppl
        #Workflow

        FormFunctionButtonControl   actionButton;
        FormActionPaneControl       actionPane;
        int                         i;
        
        // Determine if action pane control exists on form.
        for (i=1; i<=formDesign.controlCount(); i++)
        {
            if ((formDesign.controlNum(i).handle() == classNum(FormActionPaneControl)))
            {
                actionPane = formDesign.controlNum(i);
                break;
            }
        }

        // if we have an action pane, add workflow message bar group directly after it
        if (actionPane != null)
        {
            workflowActionPaneButtonGroup = actionPane.addControl(FormControlType::ButtonGroup, #WorkflowActionPaneButtonGroup);
            workflowActionPaneButtonGroup.visible(false);
            workflowActionPaneButtonGroup.dataSource(workflowDatasource.name());
            
            actionBarButtonGroup = workflowActionPaneButtonGroup.addControl(FormControlType::MenuButton, #WorkflowActionBarButtonGroup);
            actionBarButtonGroup.text("@SYS110684");
            actionBarButtonGroup.imageLocation(SysImageLocation::Symbol);
            actionBarButtonGroup.normalImage('Workflow');
            actionBarButtonGroup.needsRecord(true);
            actionBarSubmitButton = actionBarButtonGroup.addControl(FormControlType::MenuFunctionButton, #WorkflowActionBarSubmitButton);
            actionBarSubmitButton.menuItemType(MenuItemType::Action);
            actionBarSubmitButton.dataSource(workflowDatasource.name());
            actionBarSubmitButton.visible(false);
            actionBarSubmitButton.enabled(false);

            actionCount = 0;
            maxActionCount = 10;
            for (i=1; i<=maxActionCount; i++)
            {
                actionButton = actionBarButtonGroup.addControl(FormControlType::MenuFunctionButton, #WorkflowActionMenuFunctionPrefix+int2str(i));
                actionButton.menuItemType(MenuItemType::Action);
                actionButton.dataSource(workflowDatasource.name());
                if (form.name() == formStr(WorkflowWorkList))
                {
                    actionButton.registerOverrideMethod(methodStr(FormFunctionButtonControl, clicked),
                                                        identifierStr('menuItem_Clicked'),
                                                        form);
                }
                actionButton.visible(false);
                actionButton.enabled(false);
            }
        }
        
    }
}

原理解析

通过[Hookable(false), PostHandlerFor(classStr(SysWorkflowFormControls), staticMethodStr(SysWorkflowFormControls, construct))]监听SysWorkflowFormControls的类似构造函数（指一个类中可以返回类实例的静态方法，不一定非得是construct），在检测到调用的FormFormNeedsAOverride符合时，替换返回值为当前extend系统类的实例，由于extend可以同名覆盖对应函数，可以实现修改系统类的目标（在满足特定条件时，将系统调用系统类的代码控制流引导至我们的自定义类中，并可以缺省其他不需要修改的函数），实现灵活的系统类逻辑修改，且不对非目标调用的窗体产生影响。