#region Autodesk.Revit.DB.Structure.LoadUsage.Create(Autodesk.Revit.DB.Document,string)
#region Autodesk.Revit.DB.Structure.LoadComponent.#ctor(Autodesk.Revit.DB.ElementId,System.Double)
#region Autodesk.Revit.DB.Structure.LoadCombination.SetComponents(System.Collections.Generic.IList{Autodesk.Revit.DB.Structure.LoadComponent})
#region Autodesk.Revit.DB.Structure.LoadCombination.SetUsageIds(System.Collections.Generic.IList{Autodesk.Revit.DB.ElementId})
LoadCombination CreateLoadCombinationLoadCaseLoadUsageLoadNatureAndLoadComponent(Document document)
{
    // Create a new load combination
    LoadCombination loadCombination = LoadCombination.Create(document, "DL1 + RAIN1", LoadCombinationType.Combination, LoadCombinationState.Ultimate);
    if (loadCombination == null)
       throw new Exception("Create new load combination failed.");

    // Get all existing LoadCase
    FilteredElementCollector collector = new FilteredElementCollector(document);
    ICollection<Element> collection = collector.OfClass(typeof(LoadCase)).ToElements();

    // Find LoadCase "DL1"
    LoadCase case1 = null;
    foreach (Element e in collection)
    {
       LoadCase loadCase = e as LoadCase;
       if (loadCase.Name == "DL1")
       {
          case1 = loadCase;
          break;
       }
    }

    // Get all existing LoadNature
    collector = new FilteredElementCollector(document);
    collection = collector.OfClass(typeof(LoadNature)).ToElements();

    // Find LoadNature "Dead"
    LoadNature nature1 = null;
    foreach (Element e in collection)
    {
       LoadNature loadNature = e as LoadNature;
       if (loadNature.Name == "Dead")
       {
          nature1 = loadNature;
          break;
       }
    }

    // Create LoadNature "Dead" if not exist
    if (nature1 == null)
       nature1 = LoadNature.Create(document, "Dead");

    // Create LoadCase "DL1" if not exist
    if (case1 == null)
       case1 = LoadCase.Create(document, "DL1", nature1.Id, LoadCaseCategory.Dead);

    // Create LoadNature "Rain"
    LoadNature nature2 = LoadNature.Create(document, "Rain");
    if (nature2 == null)
       throw new Exception("Create new load nature failed.");

    // Create LoadCase "RAIN1"
    LoadCase case2 = LoadCase.Create(document, "RAIN1", nature2.Id, LoadCaseCategory.Snow);
    if (case1 == null || case2 == null)
       throw new Exception("Create new load case failed.");

    // Create LoadComponents - they consist of LoadCases or nested LoadCombination and Factors
    List<LoadComponent> components = new List<LoadComponent>();
    components.Add(new LoadComponent(case1.Id, 2.0));
    components.Add(new LoadComponent(case2.Id, 1.5));

    // Add components to combination
    loadCombination.SetComponents(components);

    // Create LoadUsages
    LoadUsage usage1 = LoadUsage.Create(document, "Frequent");
    LoadUsage usage2 = LoadUsage.Create(document, "Rare");

    if (usage1 == null || usage2 == null)
       throw new Exception("Create new load usage failed.");

    // Add load usages to combination
    loadCombination.SetUsageIds(new List<ElementId>() {usage1.Id, usage2.Id});

    // Give the user some information
    TaskDialog.Show("Revit", string.Format("Load Combination ID='{0}' created successfully.", loadCombination.Id.IntegerValue));

    return loadCombination;
}
#endregion
#endregion
#endregion
#endregion

#Region "Autodesk.Revit.DB.Structure.LoadUsage.Create(Autodesk.Revit.DB.Document,string)"
#Region "Autodesk.Revit.DB.Structure.LoadComponent.#ctor(Autodesk.Revit.DB.ElementId,System.Double)"
#Region "Autodesk.Revit.DB.Structure.LoadCombination.SetComponents(System.Collections.Generic.IList{Autodesk.Revit.DB.Structure.LoadComponent})"
#Region "Autodesk.Revit.DB.Structure.LoadCombination.SetUsageIds(System.Collections.Generic.IList{Autodesk.Revit.DB.ElementId})"
        Private Function CreateLoadCombinationLoadCaseLoadUsageLoadNatureAndLoadComponent(document As Document) As LoadCombination
            ' Create a new load combination
            Dim loadCombination__1 As LoadCombination = LoadCombination.Create(document, "DL1 + RAIN1", LoadCombinationType.Combination, LoadCombinationState.Ultimate)
            If loadCombination__1 Is Nothing Then
                Throw New Exception("Create new load combination failed.")
            End If

            ' Get all existing LoadCase
            Dim collector As New FilteredElementCollector(document)
            Dim collection As ICollection(Of Element) = collector.OfClass(GetType(LoadCase)).ToElements()

            ' Find LoadCase "DL1"
            Dim case1 As LoadCase = Nothing
            For Each e As Element In collection
                Dim loadCase__2 As LoadCase = TryCast(e, LoadCase)
                If loadCase__2.Name = "DL1" Then
                    case1 = loadCase__2
                    Exit For
                End If
            Next

            ' Get all existing LoadNature
            collector = New FilteredElementCollector(document)
            collection = collector.OfClass(GetType(LoadNature)).ToElements()

            ' Find LoadNature "Dead"
            Dim nature1 As LoadNature = Nothing
            For Each e As Element In collection
                Dim loadNature__3 As LoadNature = TryCast(e, LoadNature)
                If loadNature__3.Name = "Dead" Then
                    nature1 = loadNature__3
                    Exit For
                End If
            Next

            ' Create LoadNature "Dead" if not exist
            If nature1 Is Nothing Then
                nature1 = LoadNature.Create(document, "Dead")
            End If

            ' Create LoadCase "DL1" if not exist
            If case1 Is Nothing Then
                case1 = LoadCase.Create(document, "DL1", nature1.Id, LoadCaseCategory.Dead)
            End If

            ' Create LoadNature "Rain"
            Dim nature2 As LoadNature = LoadNature.Create(document, "Rain")
            If nature2 Is Nothing Then
                Throw New Exception("Create new load nature failed.")
            End If

            ' Create LoadCase "RAIN1"
            Dim case2 As LoadCase = LoadCase.Create(document, "RAIN1", nature2.Id, LoadCaseCategory.Snow)
            If case1 Is Nothing OrElse case2 Is Nothing Then
                Throw New Exception("Create new load case failed.")
            End If

            ' Create LoadComponents - they consist of LoadCases or nested LoadCombination and Factors
            Dim components As New List(Of LoadComponent)()
            components.Add(New LoadComponent(case1.Id, 2.0))
            components.Add(New LoadComponent(case2.Id, 1.5))

            ' Add components to combination
            loadCombination__1.SetComponents(components)

            ' Create LoadUsages
            Dim usage1 As LoadUsage = LoadUsage.Create(document, "Frequent")
            Dim usage2 As LoadUsage = LoadUsage.Create(document, "Rare")

            If usage1 Is Nothing OrElse usage2 Is Nothing Then
                Throw New Exception("Create new load usage failed.")
            End If

            ' Add load usages to combination
            loadCombination__1.SetUsageIds(New List(Of ElementId)() From {
                usage1.Id,
                usage2.Id
            })

            ' Give the user some information
            TaskDialog.Show("Revit", String.Format("Load Combination ID='{0}' created successfully.", loadCombination__1.Id.IntegerValue))

            Return loadCombination__1
        End Function
#End Region
#End Region
#End Region
#End Region