Adds two stacked items to the panel. 
   Namespace:   Autodesk.Revit.UI  
  Assembly:   RevitAPIUI  (in RevitAPIUI.dll) Version: 17.0.0.0 (17.0.1090.0) 
  Since:  2011 
Syntax
| C# | 
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| Visual Basic | 
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| Visual C++ | 
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Parameters
- item1
 -  Type:  Autodesk.Revit.UI RibbonItemData  
Data containing information about the first item. This data must be of type PushButtonData, PulldownButtonData, SplitButtonData, ComboBoxData, or TextBoxData. 
- item2
 -  Type:  Autodesk.Revit.UI RibbonItemData  
Data containing information about the second item. This data must be of type PushButtonData, PulldownButtonData, SplitButtonData, ComboBoxData, or TextBoxData. 
Return Value
A collection containing the added items.Remarks
 Each new item may either be a PushButton, PulldownButton, SplitButton, ComboBox or TextBox, depending upon the type of data passed in for each argument. The new items will be created as small-size horizontal controls, with the first stacked on top of the second in the panel. 
 Exceptions
| Exception | Condition | 
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| Autodesk.Revit.Exceptions ArgumentNullException | Thrown when item1 or item2 is a null reference ( Nothing in Visual Basic) . | 
| Autodesk.Revit.Exceptions ArgumentException | Thrown when an item with the item1.Name or item2.Name already exists in the panel or the data is not of the correct type. |