Adds a Ribbon item to the panel. 
   Namespace:   Autodesk.Revit.UI  
  Assembly:   RevitAPIUI  (in RevitAPIUI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2011 
Syntax
| C# | 
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| Visual Basic | 
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| Visual C++ | 
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Parameters
- itemData
-  Type:  Autodesk.Revit.UI RibbonItemData  
 Data containing information about the new item.
Return Value
The added Ribbon item.Remarks
 The new item may either be a PushButton, PulldownButton, SplitButon, RadioButtonGroup, ComboBox, or TextBox depending upon the type of data passed in. The new item may be created as a large-size vertical control in the panel. 
 Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions ArgumentNullException | Thrown when itemData is a null reference ( Nothing in Visual Basic) . | 
| Autodesk.Revit.Exceptions ArgumentException | Thrown when an item with the itemData.Name already exists in the panel or the data is not of the correct type. |