class MyStartEventListener
{
    Eplan.EplApi.ApplicationFramework.EventHandler m_myHandler = new Eplan.EplApi.ApplicationFramework.EventHandler();

    public MyStartEventListener()
    {
        m_myHandler.SetEvent("Eplan.EplApi.OnMainStart");
        m_myHandler.EplanEvent += MyHandler_EplanEvent;
    }

    private void MyHandler_EplanEvent(IEventParameter iEventParameter)
    {
        MyGuiHandlingClass myGuiHandlingClass = new MyGuiHandlingClass();
        // Add your multilingual ribbon items on P8 application start.
        // The current display language determines the language of your ribbon items in GUI.
        myGuiHandlingClass.AddGuiElements();
    }
}


class MyEndEventListener
{
    Eplan.EplApi.ApplicationFramework.EventHandler m_myHandler = new Eplan.EplApi.ApplicationFramework.EventHandler();
    public MyEndEventListener()
    {
        m_myHandler.SetEvent("Eplan.EplApi.OnMainEnd");
        m_myHandler.EplanEvent += MyHandler_EplanEvent;
    }

    private void MyHandler_EplanEvent(IEventParameter iEventParameter)
    {
        MyGuiHandlingClass myGuiHandlingClass = new MyGuiHandlingClass();
        // Remove your multilingual ribbon items when closing the application.
        myGuiHandlingClass.RemoveGuiElements();
    }
}


public class AddInModule : IEplAddIn
{
    private MyStartEventListener m_StartEventHandler;
    private MyEndEventListener m_EndEventHandler;

    public bool OnRegister(ref System.Boolean bLoadOnStart)
    {
        bLoadOnStart = true;

        return true;
    }

    public bool OnUnregister()
    {
        return true;
    }

    public bool OnInit()
    {
        m_StartEventHandler = new MyStartEventListener();
        m_EndEventHandler = new MyEndEventListener();

        return true;
    }

    public bool OnInitGui()
    {
        return true;

    }

    public bool OnExit()
    {
        return true;
    }
}


public class MyGuiHandlingClass
{
    private const string m_tabNameEng = "My English tab";
    private const string m_tabNameGer = "Mein deutscher Tab";

    public void AddGuiElements()
    {
        // Perpare the multilingual texts.
        MultiLangString tabName = new MultiLangString();
        tabName.AddString(ISOCode.Language.L_en_US, m_tabNameEng);
        tabName.AddString(ISOCode.Language.L_de_DE, m_tabNameGer);

        MultiLangString CGName = new MultiLangString();
        CGName.AddString(ISOCode.Language.L_en_US, "English CG");
        CGName.AddString(ISOCode.Language.L_de_DE, "Deutsche CG");

        MultiLangString buttonText = new MultiLangString();
        buttonText.AddString(ISOCode.Language.L_en_US, "My English button");
        buttonText.AddString(ISOCode.Language.L_de_DE, "Mein deutscher Button");

        MultiLangString buttonDescription = new MultiLangString();
        buttonDescription.AddString(ISOCode.Language.L_en_US, "This is the description of my English button.");
        buttonDescription.AddString(ISOCode.Language.L_de_DE, "Dies ist die Beschreibung meines deutschen Buttons.");

        MultiLangString buttonTooltip = new MultiLangString();
        buttonTooltip.AddString(ISOCode.Language.L_en_US, "This is the tooltip for my English button.");
        buttonTooltip.AddString(ISOCode.Language.L_de_DE, "Dies ist der Tooltip meines deutschen Buttons.");

        // Set up your multilingual ribbon items and add them to the ribbon bar.
        RibbonTab tab = new RibbonBar().AddTab(tabName, 1);
        RibbonCommandGroup CG = tab.AddCommandGroup(CGName, 0);

        string buttonAction = "Action1";
        RibbonCommandInfo commandInfo = new RibbonCommandInfo("dummy button text", buttonAction);
        // The multilingual button text is used over the language-insensitive button text
        // from the RibbonCommandInfo constructor.

        commandInfo.MultiLangButtonText = buttonText;
        commandInfo.MultiLangDescription = buttonDescription;
        commandInfo.MultiLangTooltip = buttonTooltip;
        commandInfo.Icon = new RibbonIcon(CommandIcon.Circle_1);
        commandInfo.IndexButtonPosition = 0;

        CG.AddCommand(commandInfo);
    }

    public void RemoveGuiElements()
    {
        var ribbonBar = new RibbonBar();

        var tab = ribbonBar.GetTab(m_tabNameEng) ?? ribbonBar.GetTab(m_tabNameGer);
        tab?.Remove();
    }
}