Truss CreateTruss(Autodesk.Revit.DB.Document document, 
    FamilyInstance column1, FamilyInstance column2)
{
    Truss truss = null;
    using (Transaction transaction = new Transaction(document, "Add Truss"))
    {
       if (transaction.Start() == TransactionStatus.Started)
       {
           //sketchPlane
           XYZ origin = new XYZ(0, 0, 0);
           XYZ xDirection = new XYZ(1, 0, 0);
           XYZ yDirection = new XYZ(0, 1, 0);
           XYZ zDirection = new XYZ(0, 0, 1);
           Plane plane = Plane.Create(new Frame(origin, xDirection, yDirection, zDirection));
           SketchPlane sketchPlane = SketchPlane.Create (document, plane);

           //new base Line - use line that spans two selected columns
           AnalyticalElement frame1 = document.GetElement(
            AnalyticalToPhysicalAssociationManager.GetAnalyticalToPhysicalAssociationManager(document)
            .GetAssociatedElementId(column1.Id))
        as AnalyticalElement;
            XYZ centerPoint1 = (frame1.GetCurve() as Line).GetEndPoint(0);

           AnalyticalElement frame2 = document.GetElement(
            AnalyticalToPhysicalAssociationManager.GetAnalyticalToPhysicalAssociationManager(document)
            .GetAssociatedElementId(column2.Id))
        as AnalyticalElement;
            XYZ centerPoint2 = (frame2.GetCurve() as Line).GetEndPoint(0);

           XYZ startPoint = new XYZ(centerPoint1.X, centerPoint1.Y, 0);
           XYZ endPoint = new XYZ(centerPoint2.X, centerPoint2.Y, 0);
           Autodesk.Revit.DB.Line baseLine = null;

           try
           {
               baseLine = Line.CreateBound(startPoint, endPoint);
           }
           catch (System.ArgumentException)
           {
               throw new Exception("Selected columns are too close to create truss.");
           }

           // use the active view for where the truss's tag will be placed; View used in
           // NewTruss should be plan or elevation view parallel to the truss's base line 
           Autodesk.Revit.DB.View view = document.ActiveView;

           // Get a truss type for the truss
           FilteredElementCollector collector = new FilteredElementCollector(document);
           collector.OfClass(typeof(FamilySymbol));
           collector.OfCategory(BuiltInCategory.OST_Truss);

           TrussType trussType = collector.FirstElement() as TrussType;

           if (null != trussType)
           {
               truss = Truss.Create(document, trussType.Id, sketchPlane.Id, baseLine);
               transaction.Commit();
           }
           else
           {
               transaction.RollBack();
               throw new Exception("No truss types found in document.");
           }
       }
    }

    return truss;
}

Private Function CreateTruss(document As Autodesk.Revit.DB.Document, column1 As FamilyInstance, column2 As FamilyInstance) As Truss
   Dim truss__1 As Truss = Nothing
   Using transaction As New Transaction(document, "Add Truss")
      If transaction.Start() = TransactionStatus.Started Then
         'sketchPlane
         Dim origin As New XYZ(0, 0, 0)
         Dim xDirection As New XYZ(1, 0, 0)
         Dim yDirection As New XYZ(0, 1, 0)
         Dim zDirection As New XYZ(0, 0, 1)
         Dim planeFrame As New Autodesk.Revit.DB.Frame(origin, xDirection, yDirection, zDirection)
         Dim plane As Plane = Autodesk.Revit.DB.Plane.Create(planeFrame)
         Dim sketchPlane__2 As SketchPlane = SketchPlane.Create(document, plane)
         'new base Line - use line that spans two selected columns
         Dim locFrame1 As LocationCurve = TryCast(column1.Location, LocationCurve)
         Dim centerPoint1 As XYZ = TryCast(locFrame1.Curve, Line).GetEndPoint(0)

         Dim locFrame2 As LocationCurve = TryCast(column2.Location, LocationCurve)
         Dim centerPoint2 As XYZ = TryCast(locFrame2.Curve, Line).GetEndPoint(0)
         Dim startPoint As New XYZ(centerPoint1.X, centerPoint1.Y, 0)
         Dim endPoint As New XYZ(centerPoint2.X, centerPoint2.Y, 0)
         Dim baseLine As Autodesk.Revit.DB.Line = Nothing

         Try
            baseLine = Line.CreateBound(startPoint, endPoint)
         Catch generatedExceptionName As System.ArgumentException
            Throw New Exception("Selected columns are too close to create truss.")
         End Try

         ' use the active view for where the truss's tag will be placed; View used in
         ' NewTruss should be plan or elevation view parallel to the truss's base line 
         Dim view As Autodesk.Revit.DB.View = document.ActiveView

         ' Get a truss type for the truss
         Dim collector As New FilteredElementCollector(document)
         collector.OfClass(GetType(FamilySymbol))
         collector.OfCategory(BuiltInCategory.OST_Truss)

         Dim trussType As TrussType = TryCast(collector.FirstElement(), TrussType)

         If trussType IsNot Nothing Then
            truss__1 = Truss.Create(document, trussType.Id, sketchPlane__2.Id, baseLine)
            transaction.Commit()
         Else
            transaction.RollBack()
            Throw New Exception("No truss types found in document.")
         End If
      End If
   End Using

   Return truss__1
End Function