How do I draw the Y axis at the middle of the X axis?

You can draw the Y axis at any custom position by using ChartAxisLocationType class. You have to set the type of the location as Set for the Y axis. By setting the LocationType as set you can change the location of the axis manually.

C#

// Drawing Y axis mid of the X axis

this.chartControl1.PrimaryYAxis.LocationType = ChartAxisLocationType.Set;

this.chartControl1.PrimaryYAxis.Location = new PointF(300, 352);

VB

'' Drawing Y axis mid of the X axis

Me.chartControl1.PrimaryYAxis.LocationType=ChartAxisLocationType.Set

Me.chartControl1.PrimaryYAxis.Location = New PointF(300, 352)

Please refer the sample in the below link which illustrates the above:

http://websamples.syncfusion.com/samples/KB/Chart.Windows/ChartSample/main.htm