How to build form by code Dynamics AX 2012

    Form                   form;
    FormRun             formRun;
    Args                    args;
    FormBuildDesign         formBuildDesign;
    FormBuildControl        formBuildControl;
    FormBuildTabControl     formBuildTabControl;
    FormBuildTabPageControl formBuildTabPageControl;
    FormBuildGridControl    formBuildGridControl;
    FormBuildDatasource     formBuildDatasource;
    FormBuildStringControl  formString;
    ;

    form = new Form();
    formBuildDatasource = form.addDataSource(tableStr(PurchTable));
    formBuildDesign = form.addDesign('design');
    formBuildTabControl = formBuildDesign.addControl(FormControlType::Tab, 'Tab');
    formBuildTabPageControl = formBuildTabControl.addControl(FormControlType::TabPage, 'TabPage');
    formBuildGridControl = formBuildTabPageControl.addControl(FormControlType::Grid, 'Grid');
    formString = formBuildGridControl.addDataField(formBuildDatasource.id(), fieldNum(PurchTable, PurchId));
    formString.label("PurchId");

    args    = new Args();
    args.object(form);
    formRun = classFactory.formRunClass(args);
    formRun.init();
    formRun.run();
    formRun.wait();