Zoom to Layer by Index Number Snippet

///<summary>Zooms to the specified layer in the active view at a specific index number.</summary>
/// 
///<param name="activeView">An IActiveView interface</param>
///<param name="layerIndex">A System.Int32 that is the index number of the layer to zoom to. Example: 0</param>
///  
///<remarks>Index number 0 is the first layer in the Active View.</remarks>
public void ZoomToLayerByIndexNumber(ESRI.ArcGIS.Carto.IActiveView activeView, System.Int32 layerIndex)
{

  if (activeView == null || layerIndex < 0)
  {
    return;
  }
  ESRI.ArcGIS.Carto.IMap map = activeView.FocusMap;

  // Ensure the layer is available(layerIndex is 0-based)
  if (layerIndex >= map.LayerCount)
  {
    return;
  }

  // Refresh and Zoom to the layer
  activeView.Extent = map.get_Layer(layerIndex).AreaOfInterest;
  activeView.Refresh();
}

'''<summary>Zooms to the specified layer in the active view at a specific index number.</summary>
''' 
'''<param name="activeView">An IActiveView interface</param>
'''<param name="layerIndex">A System.Int32 that is the index number of the layer to zoom to. Example: 0</param>
'''  
'''<remarks>Index number 0 is the first layer in the Active View.</remarks>
Public Sub ZoomToLayerByIndexNumber(ByVal activeView As ESRI.ArcGIS.Carto.IActiveView, ByVal layerIndex As System.Int32)

  If activeView Is Nothing OrElse layerIndex < 0 Then
  	Return
  End If

  Dim map As ESRI.ArcGIS.Carto.IMap = activeView.FocusMap

  ' Ensure the layer is available(layerIndex is 0-based)
  If layerIndex >= map.LayerCount Then
	  Return
  End If

  ' Refresh and Zoom to the layer
  activeView.Extent = map.Layer(layerIndex).AreaOfInterest
  activeView.Refresh()

End Sub