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

{
  // Note: Needs QueuedTask to run
  {
    //Set properties for Camera
    CIMViewCamera cimCamera = new()
    {
      X = camera.X,
      Y = camera.Y,
      Z = camera.Z,
      Scale = camera.Scale,
      Pitch = camera.Pitch,
      Heading = camera.Heading,
      Roll = camera.Roll
    };

    //Create new CIM bookmark and populate its properties
    var cimBookmark = new CIMBookmark() { Camera = cimCamera, Name = cameraName, ThumbnailImagePath = "" };

    //Add a new bookmark for the active map.
    mapView.Map.AddBookmark(cimBookmark);
  }
}

{
  // Note : Needs QueuedTask to run
  {
    //Get the bookmark's definition
    var bookmarkDef = oldBookmark.GetDefinition();

    //Modify the bookmark's location
    bookmarkDef.Location = envelope;

    //Clear the camera as it is no longer valid.
    bookmarkDef.Camera = null;

    //Set the bookmark definition
    oldBookmark.SetDefinition(bookmarkDef);
  }
}