public Result OnStartup(UIControlledApplication application)
{
    // add new ribbon panel
    RibbonPanel ribbonPanel = application.CreateRibbonPanel("NewRibbonPanel");

    //Create a push button in the ribbon panel �NewRibbonPanel"
    string assembly = @"D:\Sample\HelloWorld\bin\Debug\HelloWorld.dll";
    PushButton pushButton = ribbonPanel.AddItem(new PushButtonData("Hello Button", 
        "Hello Button", assembly, "Hello.HelloButton")) as PushButton;

    // create bitmap image for button
    Uri uriImage = new Uri(@"D:\Sample\HelloWorld\bin\Debug\39-Globe_32x32.png");
    BitmapImage largeImage = new BitmapImage(uriImage);

    // assign bitmap to button
    pushButton.LargeImage = largeImage;

    // assign a small bitmap to button which is used if command
    // is moved to Quick Access Toolbar
    Uri uriSmallImage = new Uri(@"D:\Sample\HelloWorld\bin\Debug\39-Globe_16x16.png");
    BitmapImage smallImage = new BitmapImage(uriSmallImage);

    // assign small image to button
    pushButton.Image = smallImage;

    // add a vertical separator bar to the panel
    ribbonPanel.AddSeparator();

    // define 3 new buttons to be added as stacked buttons
    PushButtonData buttonRed = new PushButtonData ("Hello Red", "Hello Red", 
        assembly, "Hello.HelloRed");
    buttonRed.Image = new BitmapImage(new Uri(@"D:\Sample\HelloWorld\bin\Debug\Red.bmp"));
    PushButtonData buttonBlue = new PushButtonData("Hello Blue", "Hello Blue", 
        assembly, "Hello.HelloBlue");
    buttonBlue.Image = new BitmapImage(new Uri(@"D:\Sample\HelloWorld\bin\Debug\Blue.bmp"));
    PushButtonData buttonGreen = new PushButtonData("Hello Green", "Hello Green", 
        assembly, "Hello.HelloGreen");
    buttonGreen.Image =
        new BitmapImage(new Uri(@"D:\Sample\HelloWorld\bin\Debug\Green.bmp"));

    // add 3 stacked buttons to the panel
    ribbonPanel.AddStackedItems(buttonRed, buttonBlue, buttonGreen);

    // add a pull-down button to the panel 
    PulldownButton pulldownButton = ribbonPanel.AddItem(new PulldownButtonData("Hello", 
        "Hello 123")) as PulldownButton;
    pulldownButton.LargeImage =
        new BitmapImage(new Uri(@"D:\Sample\HelloWorld\bin\Debug\Hello.bmp"));

    // add some menu items to the pull-down button and assign bitmaps to them
    PushButton buttonOne = pulldownButton.AddPushButton(new PushButtonData("Hello One", 
        "Hello 123", assembly, "Hello.HelloOne"));
    buttonOne.LargeImage =
        new BitmapImage(new Uri(@"D:\Sample\HelloWorld\bin\Debug\One.bmp"));
    PushButton buttonTwo = pulldownButton.AddPushButton(new PushButtonData("Hello Two", 
        "Hello 123", assembly, "Hello.HelloTwo"));
    buttonTwo.LargeImage =
        new BitmapImage(new Uri(@"D:\Sample\HelloWorld\bin\Debug\Two.bmp"));
    PushButton buttonThree = pulldownButton.AddPushButton(new PushButtonData("Hello Three", 
        "Hello 123", assembly, "Hello.HelloThree"));
    buttonThree.LargeImage =
        new BitmapImage(new Uri(@"D:\Sample\HelloWorld\bin\Debug\Three.bmp"));

    return Result.Succeeded;
}

Public Function OnStartup(application As UIControlledApplication) As Autodesk.Revit.UI.Result Implements IExternalApplication.OnStartup
    ' add new ribbon panel
    Dim ribbonPanel As RibbonPanel = application.CreateRibbonPanel("NewRibbonPanel")

    'Create a push button in the ribbon panel �NewRibbonPanel"
    Dim assembly As String = "D:\Sample\HelloWorld\bin\Debug\HelloWorld.dll"
    Dim pushButton As PushButton = TryCast(ribbonPanel.AddItem(New PushButtonData("Hello Button", "Hello Button", assembly, "Hello.HelloButton")), PushButton)

    ' create bitmap image for button
    Dim uriImage As New Uri("D:\Sample\HelloWorld\bin\Debug\39-Globe_32x32.png")
    Dim largeImage As New BitmapImage(uriImage)

    ' assign bitmap to button
    pushButton.LargeImage = largeImage

    ' assign a small bitmap to button which is used if command
    ' is moved to Quick Access Toolbar
    Dim uriSmallImage As New Uri("D:\Sample\HelloWorld\bin\Debug\39-Globe_16x16.png")
    Dim smallImage As New BitmapImage(uriSmallImage)

    ' assign small image to button
    pushButton.Image = smallImage

    ' add a vertical separator bar to the panel
    ribbonPanel.AddSeparator()

    ' define 3 new buttons to be added as stacked buttons
    Dim buttonRed As New PushButtonData("Hello Red", "Hello Red", assembly, "Hello.HelloRed")
    buttonRed.Image = New BitmapImage(New Uri("D:\Sample\HelloWorld\bin\Debug\Red.bmp"))
    Dim buttonBlue As New PushButtonData("Hello Blue", "Hello Blue", assembly, "Hello.HelloBlue")
    buttonBlue.Image = New BitmapImage(New Uri("D:\Sample\HelloWorld\bin\Debug\Blue.bmp"))
    Dim buttonGreen As New PushButtonData("Hello Green", "Hello Green", assembly, "Hello.HelloGreen")
    buttonGreen.Image = New BitmapImage(New Uri("D:\Sample\HelloWorld\bin\Debug\Green.bmp"))

    ' add 3 stacked buttons to the panel
    ribbonPanel.AddStackedItems(buttonRed, buttonBlue, buttonGreen)

    ' add a pull-down button to the panel 
    Dim pulldownButton As PulldownButton = TryCast(ribbonPanel.AddItem(New PulldownButtonData("Hello", "Hello 123")), PulldownButton)
    pulldownButton.LargeImage = New BitmapImage(New Uri("D:\Sample\HelloWorld\bin\Debug\Hello.bmp"))

    ' add some menu items to the pull-down button and assign bitmaps to them
    Dim buttonOne As PushButton = pulldownButton.AddPushButton(New PushButtonData("Hello One", "Hello 123", assembly, "Hello.HelloOne"))
    buttonOne.LargeImage = New BitmapImage(New Uri("D:\Sample\HelloWorld\bin\Debug\One.bmp"))
    Dim buttonTwo As PushButton = pulldownButton.AddPushButton(New PushButtonData("Hello Two", "Hello 123", assembly, "Hello.HelloTwo"))
    buttonTwo.LargeImage = New BitmapImage(New Uri("D:\Sample\HelloWorld\bin\Debug\Two.bmp"))
    Dim buttonThree As PushButton = pulldownButton.AddPushButton(New PushButtonData("Hello Three", "Hello 123", assembly, "Hello.HelloThree"))
    buttonThree.LargeImage = New BitmapImage(New Uri("D:\Sample\HelloWorld\bin\Debug\Three.bmp"))

    Return Result.Succeeded
End Function