Found out that once I add HeaderSeparator to my custom Legend object and handle the chat object's CustomizeLegend event it worked as I wanted. The custom items are displayed on separate rows. Here are the changes that I did.
chart.Legends.Add(new Legend
{
LegendStyle = LegendStyle.Table,
BorderColor = Color.Black,
BorderWidth = 1,
BorderDashStyle = ChartDashStyle.Solid,
Alignment = StringAlignment.Center,
DockedToChartArea = areaCounter.ToString(),
Docking = Docking.Bottom,
Name = "CustomLegend",
IsTextAutoFit = true,
InterlacedRows = true,
TableStyle = LegendTableStyle.Tall,
HeaderSeparator = LegendSeparatorStyle.Line,
HeaderSeparatorColor = Color.Gray,
IsDockedInsideChartArea = false
});
LegendItem newItem3 = new LegendItem();
var strVal = item.Value;
foreach (var val in strVal)
{
newItem3.Cells.Add(LegendCellType.Text, val, ContentAlignment.BottomCenter);
}
chart.Legends["CustomLegend"].CustomItems.Add(newItem3);
chart.CustomizeLegend += chart_CustomizeLegend;
void chart_CustomizeLegend(object sender, CustomizeLegendEventArgs e)
{
Chart chart = sender as Chart;
if (chart == null) return;
foreach (var item in e.LegendItems)
{
item.SeparatorType = LegendSeparatorStyle.Line;
item.SeparatorColor = Color.Black;
}
}