X++

Apparently you cannot populate a form data group runtime in AX. I have been able to overcome the issue by adding the controls dynamically. In this example I have created a form with InventTable as the datasource, and added a FormGroupControl called FormDataGroup with AutoDeclare = Yes. Then I have overridden the executeQuery() on InventTable_ds to call my custom method stored on the form. Here is the source to add AX FormGroupControl runtime from code:

public void WIK_addFieldGroup()
{
    #AOT
    #Properties

    TreeNode            fieldGroupRoot = TreeNode::findNode(strFmt('%1\\%2\\Field Groups\\%3',
        #TablesPath,
        tableStr(InventTable),
        tableFieldgroupStr(InventTable, Name)));
    TreeNodeIterator    tni = fieldGroupRoot.AOTiterator();
    TreeNode            fieldGroupNode = tni ? tni.next() : null;
    int                 fieldNo;
    DictField           dictField;
    FormControlType     controlType;
    Object              formControl;
        
    formDataGroup.hideIfEmpty(false);
    formDataGroup.caption(fieldGroupRoot.AOTgetProperty(#PropertyLabel));
    
    while (fieldGroupNode)
    {
        fieldNo = (select firstOnly AxId from SysModelElement
            where  SysModelElement.ParentId     == tableNum(InventTable)
                && SysModelElement.ElementType  == UtilElementType::TableField
                && SysModelElement.Name         == fieldGroupNode.AOTname()).AxId;
        
        dictField = new DictField(tableNum(InventTable), fieldNo);
        
        if (!dictField)
        {
            // display method in field group
            fieldGroupNode = tni.next();
            continue;
        }
        
        switch (dictField.baseType())
        {
            case Types::Int64 :
                controlType = FormControlType::Int64;
                break;
            case Types::Integer :
                controlType = FormControlType::Integer;
                break;
            case Types::String :
                controlType = FormControlType::String;
                break;
            case Types::Date :
                controlType = FormControlType::Date;
                break;
            case Types::UtcDateTime :
                controlType = FormControlType::DateTime;
                break;
                
            //TODO: Implement all field types
        }

        formControl = formdatagroup.addControl(controlType, strFmt('InventTable_%1', fieldGroupNode.AOTname()));
        formControl.dataSource(InventTable_ds.id());
        formControl.dataField(fieldNo);
        formControl.label(dictField.label());

        fieldGroupNode = tni.next();
    }
}