public void DivideSurface(Document document, Form form)
{
    Autodesk.Revit.ApplicationServices.Application application = document.Application;
    Options opt = application.Create.NewGeometryOptions();
    opt.ComputeReferences = true;

    Autodesk.Revit.DB.GeometryElement geomElem = form.get_Geometry(opt);
    foreach (GeometryObject geomObj in geomElem)
    {
        Solid solid = geomObj as Solid;
        foreach (Face face in solid.Faces)
        {
            if (face.Reference != null)
            {
                DividedSurface ds = DividedSurface.Create(document,face.Reference);
                // create a divided surface with fixed number of U and V grid lines
                SpacingRule srU = ds.USpacingRule;
                srU.SetLayoutFixedNumber(16, SpacingRuleJustification.Center, 0, 0);

                SpacingRule srV = ds.VSpacingRule;
                srV.SetLayoutFixedNumber(24, SpacingRuleJustification.Center, 0, 0);

                break;  // just divide one face of form
            }
        }
    }
}

Public Sub DivideSurface(document As Document, form As Form)
    Dim application As Autodesk.Revit.ApplicationServices.Application = document.Application
    Dim opt As Options = application.Create.NewGeometryOptions()
    opt.ComputeReferences = True

    Dim geomElem As Autodesk.Revit.DB.GeometryElement = form.Geometry(opt)
    For Each geomObj As GeometryObject In geomElem
        Dim solid As Solid = TryCast(geomObj, Solid)
        For Each face As Face In solid.Faces
            If face.Reference IsNot Nothing Then
                Dim ds As DividedSurface = DividedSurface.Create(document, face.Reference)
                ' create a divided surface with fixed number of U and V grid lines
                Dim srU As SpacingRule = ds.USpacingRule
                srU.SetLayoutFixedNumber(16, SpacingRuleJustification.Center, 0, 0)

                Dim srV As SpacingRule = ds.VSpacingRule
                srV.SetLayoutFixedNumber(24, SpacingRuleJustification.Center, 0, 0)

                ' just divide one face of form
                Exit For
            End If
        Next
    Next
End Sub