Create number sequence in D365

• Create a new Extended Data Type (EDT)
• Create a new class that extends the NumberSeqModuleInventory class and then create the COC method to loadModule and add the following code:

[ExtensionOf(classStr(NumberSeqModuleInventory))]

final class NumberSeqModuleInventoryDOM_Extension

{

    /// <summary>

    ///    Configures all the data types that are being used by the module.

    /// </summary>

    protected void loadModule()

    {

        next loadModule();

        NumberSeqDatatype datatype = NumberSeqDatatype::construct();

        //Setup Order Id

        datatype.parmDatatypeId(extendedtypenum(DOMOrderId));

        datatype.parmReferenceHelp(literalstr("Key identifier for Order details"));

        datatype.parmWizardIsContinuous(false);

        datatype.parmWizardIsManual(NoYes::Yes);

        datatype.parmWizardIsChangeDownAllowed(NoYes::No);

        datatype.parmWizardIsChangeUpAllowed(NoYes::No);

        datatype.parmSortField(20);

        datatype.addParameterType(NumberSeqParameterType::DataArea, true, false);

        this.create(datatype);

    }

}

• Create a new extension class of table InventParameters and a new method.

[ExtensionOf(tableStr(InventParameters))]

final class InventParametersDOM_Extension

{

    public static NumberSequenceReference numRefDOMOrderId()

    {

        return NumberSeqReference::findReference(extendedTypeNum(DOMOrderId));

    }

}

• Create a runnable class NumberSeqModuleInventoryRunnableClass which will              load   the number sequences.

class NumberSeqModuleInventoryRunnableClass

{

    public static void main(Args _args)

    {

        NumberSeqModuleInventory   loadModule = new NumberSeqModuleInventory();

        ;

        loadModule.load();

    }

}

• At last, go to Organization administration – Number sequences – Number sequences – Generate Button (Run the wizard and complete it)
• Add EDT in the table
• Add field in the form

Add the following code on the Class declaration node

 NumberSeqFormHandler numberSeqFormHandler;

• Create a new method on the form and write the following code

    NumberSeqFormHandler numberSeqFormHandler()

    {

        if (!numberSeqFormHandler)

        {

            numberSeqFormHandler = NumberSeqFormHandler::newForm(

                                    NumberSeqReference::findReference(extendedtypenum(DOMOrderId)).NumberSequenceId, element,DOMOrderTable_ds,fieldnum(DOMOrderTable, OrderId));

        }

        return numberSeqFormHandler;

    }

Override the close method of the form 

    public void close()

    {

        if (numberSeqFormHandler)

        {

            numberSeqFormHandler.formMethodClose();

        }

        super();

    }

DataSource methods

        public void create(boolean _append = false)

        {

            element.numberSeqFormHandler().formMethodDataSourceCreatePre();

            super(_append);

            element.numberSeqFormHandler().formMethodDataSourceCreate(true);

        }

        public void write()

        {

            super();

            element.numberSeqFormHandler().formMethodDataSourceWrite();

        }

        public boolean validateWrite()

        {

            boolean ret;

        

            ret = super();

            ret = element.numberSeqFormHandler().formMethodDataSourceValidateWrite(ret) && ret;

        

            return ret;

        }

        public void delete()

        {

            element.numberSeqFormHandler().formMethodDataSourceDelete();

            super();

        }

        public void linkActive()

        {

            element.numberSeqFormHandler().formMethodDataSourceLinkActive();

            super();

        }

Reference :- https://www.dynamics101.com/creating-custom-number-sequences-microsoft-dynamics-ax-2012/