ExpanderView newExpander = new ExpanderView();
newExpander.Name = name;
newExpander.Header = header;
newExpander.FontSize = 40;

if (row == 0)
    newExpander.IsExpanded = true;

foreach (Item li in items)
{
     CheckBox tb = new CheckBox();
     tb.Content = content;
     tb.FontSize = 20;

     newExpander.Items.Add(tb);
}


MyGrid.Children.Add(newExpander);
Grid.SetRow(newExpander, row);

<Grid x:Name="MyGrid">
                        <Grid.RowDefinitions>
                            <RowDefinition></RowDefinition>
                            <RowDefinition></RowDefinition>
                            <RowDefinition></RowDefinition>
                            <RowDefinition></RowDefinition>
                        </Grid.RowDefinitions>
                    </Grid>

Grid.SetRow(newExpander, row);