Dynamics Community Forum Thread Details

Form control lookup extension via Chain of Command

Hi All,

I've been struggling to create a Chain of Command-based form control lookup override for a while now, and I didn't see anything on it in the forums, so I thought I'd share. First, just a reminder of the event-based approach we all know and hate (okay, maybe just I hate it .. I just don't want to use attributes on my code if I don't have to).

An example of what I'll call the "old way":

class ExampleForm_EventHandler
{
    [FormEventHandler(formStr(FormImChanging), FormEventType::Initialized)]
    public static void FormImChanging_OnInitializing(xFormRun sender, FormEventArgs e)
    {
        ExampleForm_EventHandler overrideHandler = new ExampleForm_EventHandler();

        FormStringControl targetControl = sender.control(sender.controlId(formControlStr(FormImChanging, targetControl)));
        targetControl.registerOverrideMethod(methodStr(FormDataObject, lookup), methodStr(ExampleForm_EventHandler, lookupOverride), overrideHandler);
    }

    public void lookupOverride(FormStringControl _callingControl)
    {
        SysTableLookup sysTableLookup = SysTableLookup::newParameters(tableNum(SomePertinentTable), _callingControl);

        sysTableLookup.addLookupfield(fieldNum(SomePertinentTable, UsefulField1), true);
        sysTableLookup.addLookupfield(fieldNum(SomePertinentTable, UsefulField2));

        Query q = new Query();

        q.addDataSource(tableNum(SomePertinentTable)).addRange(fieldNum(SomePertinentTable, NoYesFieldIWantToConstrain)).value(queryValue(NoYes::No));

        // Run lookup
        sysTableLookup.parmQuery(q);
        sysTableLookup.performFormLookup();
    }
}

Now, the "new way" (Chain of Command) that I finally got working today (using the same bogus names from the above code sample):

[ExtensionOf(formstr(ExampleForm))]
final class ExampleForm_FormIan_Extension
{    
    void init()
    {
        next init();
    
        //Assumes TargetControl is auto-declared, but we can get to it even if it's not
        TargetControl.registerOverrideMethod(methodStr(FormDataObject, lookup), formMethodStr(ExampleForm, ianCustomLookup));
    }

    public void ianCustomLookup(FormStringControl _callingControl)
    {
        SysTableLookup sysTableLookup = SysTableLookup::newParameters(tableNum(SomePertinentTable), _callingControl);

        sysTableLookup.addLookupfield(fieldNum(SomePertinentTable, UsefulField1), true);
        sysTableLookup.addLookupfield(fieldNum(SomePertinentTable, UsefulField2));

        Query q = new Query();

        q.addDataSource(tableNum(SomePertinentTable)).addRange(fieldNum(SomePertinentTable, NoYesFieldIWantToConstrain)).value(queryValue(NoYes::No));

        // Run lookup
        sysTableLookup.parmQuery(q);
        sysTableLookup.performFormLookup();
    }
}

Hope this helps somebody!

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