// get handle to application from document
Autodesk.Revit.ApplicationServices.Application application = document.Application;

// Create a geometry line in Revit application
XYZ startPoint = new XYZ(0, 0, 0);
XYZ endPoint = new XYZ(10, 10, 0);
Line geomLine = Line.CreateBound(startPoint, endPoint);

// Create a geometry arc in Revit application
XYZ end0 = new XYZ(1, 0, 0);
XYZ end1 = new XYZ(10, 10, 10);
XYZ pointOnCurve = new XYZ(10, 0, 0);
Arc geomArc = Arc.Create(end0, end1, pointOnCurve);

// Create a geometry plane in Revit application
XYZ origin = new XYZ(0, 0, 0);
XYZ normal = new XYZ(1, 1, 0);
Plane geomPlane = application.Create.NewPlane(normal, origin);

// Create a sketch plane in current document
SketchPlane sketch = SketchPlane.Create(document, geomPlane);

// Create a ModelLine element using the created geometry line and sketch plane
ModelLine line = document.Create.NewModelCurve(geomLine, sketch) as ModelLine;

// Create a ModelArc element using the created geometry arc and sketch plane
ModelArc arc = document.Create.NewModelCurve(geomArc, sketch) as ModelArc;

' get handle to application from document
Dim application As Autodesk.Revit.ApplicationServices.Application = document.Application

' Create a geometry line in Revit application
Dim startPoint As New XYZ(0, 0, 0)
Dim endPoint As New XYZ(10, 10, 0)
Dim geomLine As Line = Line.CreateBound(startPoint, endPoint)

' Create a geometry arc in Revit application
Dim end0 As New XYZ(1, 0, 0)
Dim end1 As New XYZ(10, 10, 10)
Dim pointOnCurve As New XYZ(10, 0, 0)
Dim geomArc As Arc = Arc.Create(end0, end1, pointOnCurve)

' Create a geometry plane in Revit application
Dim origin As New XYZ(0, 0, 0)
Dim normal As New XYZ(1, 1, 0)
Dim geomPlane As Plane = application.Create.NewPlane(normal, origin)

' Create a sketch plane in current document
Dim sketch As SketchPlane = SketchPlane.Create(document, geomPlane)

' Create a ModelLine element using the created geometry line and sketch plane
Dim line__1 As ModelLine = TryCast(document.Create.NewModelCurve(geomLine, sketch), ModelLine)

' Create a ModelArc element using the created geometry arc and sketch plane
Dim arc__2 As ModelArc = TryCast(document.Create.NewModelCurve(geomArc, sketch), ModelArc)