public sealed class NetworkDiagram : ArcGIS.Core.CoreObjectsBase, System.IDisposable  

{
  static void GetDiagram(UtilityNetwork utilityNetwork, IEnumerable<Guid> globalIDs)
  {
    Envelope extentOfInterest = MapView.Active.Map.GetDefaultExtent();

    using (DiagramManager diagramManager = utilityNetwork.GetDiagramManager())
    {
      // Get all the diagrams
      IReadOnlyList<NetworkDiagram> diagrams = diagramManager.GetNetworkDiagrams();

      // Get a diagram by name
      NetworkDiagram diagram = diagramManager.GetNetworkDiagram(_diagramName);

      // Get diagrams by extent
      diagrams = diagramManager.GetNetworkDiagrams(extentOfInterest);

      // Get diagrams from a set of utility network feature GlobalIDs
      diagrams = diagramManager.GetNetworkDiagrams(globalIDs);

      // Get diagrams from a set of utility network feature GlobalIDs within an extent
      diagrams = diagramManager.GetNetworkDiagrams(extentOfInterest, globalIDs);
    }
  }
}

{
  static List<NetworkDiagram> GetInconsistentDiagrams(UtilityNetwork utilityNetwork)
  {
    // Get the DiagramManager from the utility network
    using (DiagramManager diagramManager = utilityNetwork.GetDiagramManager())
    {
      List<NetworkDiagram> networkDiagrams = new List<NetworkDiagram>();

      // Loop through the network diagrams in the diagram manager
      foreach (NetworkDiagram diagram in diagramManager.GetNetworkDiagrams())
      {
        NetworkDiagramInfo diagramInfo = diagram.GetDiagramInfo();

        // If the diagram is not a system diagram and is in an inconsistent state, add it to our list
        if (!diagramInfo.IsSystem &&
            diagram.GetConsistencyState() != NetworkDiagramConsistencyState.DiagramIsConsistent)
        {
          networkDiagrams.Add(diagram);
        }
        else
        {
          diagram.Dispose(); // If we are not returning it we need to Dispose it
        }
      }

      return networkDiagrams;
    }
  }
}

{
  // Create a diagram layer from a NetworkDiagram
  static void CreateDiagramLayerFromNetworkDiagram(NetworkDiagram networkDiagram)
  {
    // Create the diagram map
    Map newMap = MapFactory.Instance.CreateMap(networkDiagram.Name, MapType.NetworkDiagram, MapViewingMode.Map);

    // Open the diagram map
    Task<IMapPane> mapPane = ProApp.Panes.CreateMapPaneAsync(newMap, MapViewingMode.Map);

    //Add the diagram to the map
    DiagramLayer diagramLayer = newMap.AddDiagramLayer(networkDiagram);
  }
}

{
  // Get the NetworkDiagram from a DiagramLayer and check its ConsistencyState
  static void GetDiagram(DiagramLayer diagramLayer)
  {
    NetworkDiagram diagram = diagramLayer.GetNetworkDiagram();

    // Get the consistency state from the layer
    DiagramLayerConsistencyState diagramLayerConsistencyState = diagramLayer.ConsistencyState;

    // Or from the diagram
    NetworkDiagramConsistencyState diagramConsistencyState = diagram.GetConsistencyState();
  }
}

{
  // Create a network diagram from a template and a set of utility network feature GlobalIDs
  static void CreateNetworkDiagram(UtilityNetwork utilityNetwork, IEnumerable<Guid> globalIDs)
  {
    using (DiagramManager diagramManager = utilityNetwork.GetDiagramManager())
    {
      // Get the template
      DiagramTemplate template = diagramManager.GetDiagramTemplate(TemplateName);

      // Create the diagram
      NetworkDiagram diagram = diagramManager.CreateNetworkDiagram(template, globalIDs);
    }
  }
}

{
  static void GetDiagramContent(UtilityNetwork utilityNetwork)
  {
    using (DiagramManager diagramManager = utilityNetwork.GetDiagramManager())
    {
      // Get a diagram by name
      NetworkDiagram diagram = diagramManager.GetNetworkDiagram(TemplateName);

      string jsonContent = diagram.GetContent(true, true, true, true);
    }
  }
}

{
  // Change the layout of a network diagram by querying for all the diagram elements, editing their shapes,
  static void ChangeDiagramLayout(DiagramManager diagramManager, string diagramName)
  {
    // Retrieve a diagram
    using (NetworkDiagram diagramTest = diagramManager.GetNetworkDiagram(diagramName))
    {
      // Create a DiagramElementQueryByElementTypes query object to get the diagram elements we want to work with
      DiagramElementQueryByElementTypes query = new DiagramElementQueryByElementTypes();
      query.QueryDiagramJunctionElement = true;
      query.QueryDiagramEdgeElement = true;
      query.QueryDiagramContainerElement = true;

      // Retrieve those diagram elements
      DiagramElementQueryResult elements = diagramTest.QueryDiagramElements(query);

      // Create a NetworkDiagramSubset object to edit this set of diagram elements
      NetworkDiagramSubset subset = new NetworkDiagramSubset();
      subset.DiagramJunctionElements = elements.DiagramJunctionElements;
      subset.DiagramEdgeElements = elements.DiagramEdgeElements;
      subset.DiagramContainerElements = elements.DiagramContainerElements;

      // Save the new layout of the diagram elements
      diagramTest.SaveLayout(subset, true);
    }
  }
}