Microsoft Charts - Remove Marker lines in a series

You have to define a custom property in the markup to remove the marker lines in a series

<asp:Chart ID="sampleChart" >
    <Series>
        <asp:Series Name="Default" ChartType="Area" CustomProperties="ShowMarkerLines=false">
       </asp:Series>
    </Series>
</asp:Chart>

To change the behavior in code, use the following code snippet.
sampleChart.Series["Default"]["ShowMarkerLines"] = "true";