It appears that there are no methods to plot minor grid lines. It can be accomplished using the ChartAreaPaint event. The code below shows an example.
Private
Sub _BubblePlot_ChartAreaPaint(sender As Object, e As System.Windows.Forms.PaintEventArgs) Handles _BubblePlot.ChartAreaPaint
Dim YMin As Double, YMax As Double, XMin As Double, XMax As Double, MaxStop As Double
Dim GridLoc As Double, _Increment As Double
Dim _Pen As Pen = New Pen(System.Drawing.Color.FromArgb(175, 129, 115, 27))
If (_BubblePlot.PrimaryYAxis.ValueType = ChartValueType.Logarithmic) Then 'Include Minor Gridlines for Y Axis (Horizontal)
Dim ptLeft As Point, ptRight As Point
YMin = _BubblePlot.PrimaryYAxis.Range.Min
'Min, Max Values in Log Space
YMax = _BubblePlot.PrimaryYAxis.Range.Max
MaxStop = 10 ^ YMax
Dim LogIncrement As Integer = CInt(YMin)
_Increment = 10 ^ YMin
GridLoc = _Increment
'> Draw horizonal lines incrementing by _Increment for each log cycle
Do While GridLoc < MaxStop
For I As Integer = 1 To 9
GridLoc += _Increment
ptLeft = _BubblePlot.ChartArea.GetPointByValue(
New ChartPoint(_BubblePlot.PrimaryXAxis.Range.Min, GridLoc))
ptRight = _BubblePlot.ChartArea.GetPointByValue(
New ChartPoint(_BubblePlot.PrimaryXAxis.Range.Max, GridLoc))
e.Graphics.DrawLine(_Pen, ptLeft.X, ptLeft.Y, ptRight.X, ptRight.Y)
Next
_Increment *= 10
GridLoc = _Increment
Loop
End If
If (_BubblePlot.PrimaryXAxis.ValueType = ChartValueType.Logarithmic) Then 'Include Minor Gridlines for X Axis (Vertical)
Dim ptBottom As Point, ptTop As Point
XMin = _BubblePlot.PrimaryXAxis.Range.Min
'Min, Max Values in Log Space
XMax = _BubblePlot.PrimaryXAxis.Range.Max
MaxStop = 10 ^ YMax
Dim LogIncrement As Integer = CInt(XMin)
_Increment = 10 ^ XMin
GridLoc = _Increment
'> Draw horizonal lines incrementing by _Icrement for each log cycle
Do While GridLoc < MaxStop
For I As Integer = 1 To 9
GridLoc += _Increment
ptBottom = _BubblePlot.ChartArea.GetPointByValue(
New ChartPoint(GridLoc, _BubblePlot.PrimaryYAxis.Range.Min))
ptTop = _BubblePlot.ChartArea.GetPointByValue(
New ChartPoint(GridLoc, _BubblePlot.PrimaryXAxis.Range.Max))
e.Graphics.DrawLine(_Pen, ptBottom.X, ptBottom.Y, ptTop.X, ptTop.Y)
Next
_Increment *= 10
GridLoc = _Increment
Loop
End If
End Sub
