public class CIMLayerOverrideSet : CIMObject, System.ComponentModel.INotifyPropertyChanged, System.Xml.Serialization.IXmlSerializable  

{
  //Note: Run this code within a QueuedTask
  //Get the USA States map from the project
  //This map has both States and Cities layers
  var usaMap = Project.Current.GetItems<MapProjectItem>().FirstOrDefault(m => m.Name == "USA States")?.GetMap();

  //The layout has two map frames - one for States and one for Cities
  //We will set layer visibility overrides on each map frame, so that only the relevant layer is visible in each map frame
  // Get the States map frame in the layout
  var statesMapFrame = layout.Elements.OfType<MapFrame>().FirstOrDefault(n => n.Name == "States");
  //Get the map frame definition
  var mapFrameDefinition = statesMapFrame.GetDefinition() as CIMMapFrame;
  //Enable layer visibility overrides for the states map frame
  mapFrameDefinition.OverrideLayerVisibility = true;
  //Create layer override sets
  //Set States layer to visible and Cities layer to not visible
  var layerOverrideSets = new List<CIMLayerOverrideSet>
          {
              new CIMLayerOverrideSet
              {
                  LayerURI = usaMap.Layers.FirstOrDefault(l => l.Name == "States")?.URI,
                  Value = true
              },
              new CIMLayerOverrideSet {
                  LayerURI = usaMap.Layers.FirstOrDefault(l => l.Name == "Cities")?.URI,
                  Value = false
              }
          };
  //Assign the layer override sets to the map frame definition
  mapFrameDefinition.LayerVisibilityOverrides = layerOverrideSets.ToArray();
  //Set the modified definition back to the map frame
  statesMapFrame.SetDefinition(mapFrameDefinition);

  //Next, get the cities map frame in the layout
  var citiesMapFrame = layout.Elements.OfType<MapFrame>().FirstOrDefault(n => n.Name == "Cities");
  //Get the map frame definition for the cities map frame
  var mapFrameDefinitionCities = citiesMapFrame.GetDefinition() as CIMMapFrame;
  //Enable layer visibility overrides for the cities map frame
  mapFrameDefinitionCities.OverrideLayerVisibility = true;
  //Create layer override sets for the cities map frame
  //Set Cities layer to visible and States layer to not visible
  var layerOverrideSetsCities = new List<CIMLayerOverrideSet>
          {
              new CIMLayerOverrideSet
              {
                  LayerURI = usaMap.Layers.FirstOrDefault(l => l.Name == "States")?.URI,
                  Value = false
              },
              new CIMLayerOverrideSet {
                  LayerURI = usaMap.Layers.FirstOrDefault(l => l.Name == "Cities")?.URI,
                  Value = true
              }
          };
  //Assign the layer override sets to the cities map frame definition
  mapFrameDefinitionCities.LayerVisibilityOverrides = layerOverrideSetsCities.ToArray();
  //Set the modified definition back to the cities map frame
  citiesMapFrame.SetDefinition(mapFrameDefinitionCities);
}