I tried the scatter series but it didn't work - the line and markers are not showing at all. Let's say, my underlying data has 4 columns, (Date, Price, Buy, Sell). Date is the x-axis. Date and Price will always have a value. Buy and Sell columns will have mostly nulls but at certain points will have values that match the value of the price column. So, when this chart is displayed, it will show a grey Price line with markers for Buys and Sells on this line. This works when I use a Spline Series but for Buy and Sell series I do not want to show the lines - just the markers. If I can make these lines invisible, it would be perfect. When I changed my Buy and Sell series to ScatterSeries as suggested, the series themselves were not displaying but were showing in the legend. I do not think that a scatter series will work in my specific case probably because the x-axis is a date.

Here us what I am using:

<ig:SplineSeries Name="PriceSeries" Title="PriceLocal" ItemsSource="{Binding}" ValueMemberPath="PriceLocal" XAxis="{Binding ElementName=xmXAxisDate1}" YAxis="{Binding ElementName=xmYAxisPrice}" MarkerType="None" Foreground="Gray" />

<ig:ScatterSeries Name="BuySeries" Title="Buy" ItemsSource="{Binding}" XMemberPath="AsOfDate" YMemberPath="BuyPrice" XAxis="{Binding ElementName=xmXAxisDate1}" YAxis="{Binding ElementName=xmYAxisPrice}" MarkerType="Diamond" MarkerBrush="Blue" Visibility="Visible"/>

<ig:ScatterSeries Name="SellSeries" Title="Sell" ItemsSource="{Binding}" XMemberPath="AsOfDate" YMemberPath="SellPrice" XAxis="{Binding ElementName=xmXAxisDate1}" YAxis="{Binding ElementName=xmYAxisPrice}" MarkerType="Diamond" MarkerBrush="Red" Visibility="Visible"/>