AX 365 Event handlers standard form

Get control value

var docuRef_Notes = formRun.design().controlName(formControlStr(DocuView, docuRef_Notes)) as FormStringControl;

1. Form dataSource event handler: Here I will be using the vendTable form to get table buffer and perform additional business logic or validation.
Vendtable = Form name
vendTable = form data source name
[FormDataSourceEventHandler(formDataSourceStr(Vendtable, vendTable), FormDataSourceEventType::Written)]
public static void vendTable_OnWritten(FormDataSource sender, FormDataSourceEventArgs e)
{
    FormRun                 form           = sender.formRun();
    FormDataSource          vendTable_ds =       form.dataSource(formDataSourceStr(Vendtable,Vendtable)) as FormDataSource;
   Vendtable     Vendtable= vendTable_ds.cursor();
<Now to got table buffer, perform business logic/validation>
}
lets see one more example below;

2. Form DataSource while closing the form (same will apply for OnInitialized,
[FormEventHandler(formStr(EcoResAttributeValue), FormEventType::Closing)]
public static void EcoResAttributeValue_OnClosing(xFormRun sender, FormEventArgs e)
{
     FormDataSource ecoResProduct_ds   =          sender.dataSource(formDataSourceStr(EcoResAttributeValue, EcoResProductAttributeValue));
      EcoResProductAttributeValue      ecoResAttributeValue = ecoResProduct_ds.cursor();
<YOUR CODE>
}   

3.  Post-event hander of Form init or any other standard method method
[[PostHandlerFor(formStr(Ledger), formMethodStr(Ledger, init))]
    public static void Ledger_Post_init(XppPrePostArgs _args)
    {
        #ISOCountryRegionCodes
        FormRun form = _args.getThis();
        FormDesign design = form.design();
        FormControl revaluationAccount = design.controlName(formControlStr(Ledger, revaluationAccount));
        FormControl currencyRevaluation = design.controlName(formControlStr(Ledger, currencyRevaluation));
<your code>
}

4. Form control event hander:
[FormControlEventHandler(formControlStr(LogisticsPostalAddress, Roles), FormControlEventType::Modified)]
    public static void Roles_OnModified(FormControl sender, FormControlEventArgs e)
    {
        FormRun element = sender.formRun();
        FormControl purposeCtrl   = element.design().controlName(formControlStr(LogisticsPostalAddress, Roles));
       
        FormDataSource logisticsLocation_DS = element.dataSource(formDataSourceStr(LogisticsPostalAddress, LogisticsLocation));
       <business logic>
    }