Dim myLayerCollection As ESRI.ArcGIS.Client.LayerCollection = MyMap.Layers
'Dim myLayerCount As Double = myLayerCollection.Count
'MessageBox.Show("Number of Layers in the Map:" + myLayerCount.ToString)
Dim fl As FeatureLayer
For Each l In myLayerCollection
If TypeOf (l) Is FeatureLayer Then
fl = l
fl.Visible = False
End If
Next