The SplitButton object represents a button with a clickable button appearing above a pulldown. 
   Namespace:   Autodesk.Revit.UI  
  Assembly:   RevitAPIUI  (in RevitAPIUI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2011 
Syntax
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Remarks
 Use of this class is not supported in Revit Macros. 
 Examples
private void AddSplitButton(RibbonPanel panel)
{
    string assembly = @"D:\Sample\HelloWorld\bin\Debug\HelloWorld.dll";
    // create push buttons for split button drop down
    PushButtonData bOne = new PushButtonData("ButtonNameA", "Option One",
        assembly, "Hello.HelloOne");
    bOne.LargeImage = 
        new BitmapImage(new Uri(@"D:\Sample\HelloWorld\bin\Debug\One.bmp"));
    PushButtonData bTwo = new PushButtonData("ButtonNameB", "Option Two",
        assembly, "Hello.HelloTwo");
    bTwo.LargeImage = 
        new BitmapImage(new Uri(@"D:\Sample\HelloWorld\bin\Debug\Two.bmp"));
    PushButtonData bThree = new PushButtonData("ButtonNameC", "Option Three",
        assembly, "Hello.HelloThree");
    bThree.LargeImage = 
        new BitmapImage(new Uri(@"D:\Sample\HelloWorld\bin\Debug\Three.bmp"));
    SplitButtonData sb1 = new SplitButtonData("splitButton1", "Split");
    SplitButton sb = panel.AddItem(sb1) as SplitButton;
    sb.AddPushButton(bOne);
    sb.AddPushButton(bTwo);
    sb.AddPushButton(bThree);
} Private Sub AddSplitButton(panel As RibbonPanel)
    Dim assembly As String = "D:\Sample\HelloWorld\bin\Debug\HelloWorld.dll"
    ' create push buttons for split button drop down
    Dim bOne As New PushButtonData("ButtonNameA", "Option One", assembly, "Hello.HelloOne")
    bOne.LargeImage = New BitmapImage(New Uri("D:\Sample\HelloWorld\bin\Debug\One.bmp"))
    Dim bTwo As New PushButtonData("ButtonNameB", "Option Two", assembly, "Hello.HelloTwo")
    bTwo.LargeImage = New BitmapImage(New Uri("D:\Sample\HelloWorld\bin\Debug\Two.bmp"))
    Dim bThree As New PushButtonData("ButtonNameC", "Option Three", assembly, "Hello.HelloThree")
    bThree.LargeImage = New BitmapImage(New Uri("D:\Sample\HelloWorld\bin\Debug\Three.bmp"))
    Dim sb1 As New SplitButtonData("splitButton1", "Split")
    Dim sb As SplitButton = TryCast(panel.AddItem(sb1), SplitButton)
    sb.AddPushButton(bOne)
    sb.AddPushButton(bTwo)
    sb.AddPushButton(bThree)
End Sub Inheritance Hierarchy
  System Object  
Autodesk.Revit.UI RibbonItem
Autodesk.Revit.UI RibbonButton
Autodesk.Revit.UI PulldownButton
Autodesk.Revit.UI SplitButton
 
 Autodesk.Revit.UI RibbonItem
Autodesk.Revit.UI RibbonButton
Autodesk.Revit.UI PulldownButton
Autodesk.Revit.UI SplitButton