On a VB form why are graphics disappearing when the form is first displayed? - vb.net

Question

I have a form which displays graphs of various kinds, taken from sales data from a database.
These graphs are drawn on panels on the form but I have had a very recent issue. Up until recently, the form displayed the graphs when it was displayed but now the graphs appear then disappear and I cannot figure out why.
Here is a link to a Vimeo video showing the behaviour: https://vimeo.com/575969787
When the form is loaded a procedure is called in the Form_Shown event which draws the graphs - for ease of understanding I have restricted this to one graph only.
Private Sub FormDashboard_Shown(sender As Object, e As EventArgs) Handles Me.Shown
'Once form is initialised and shown run all the reports
RunReports(True)
End Sub
Private Sub RunReports(All As Boolean)
'Display these reports
DrawDepartment(PanelFood, TableDepartment)
'DrawDepartment(PanelWine, TableDepartment)
'DrawDivision(PanelDivision, TableDepartment)
'DrawCLA(PanelCLA, TableCLA)
''If all = true then also display MAT
'If (All = True) Then
' DrawMAT(PanelMAT, TableMAT)
'End If
End Sub
Public Shared Sub DrawDepartment(TargetPanel As Panel, TableGraph As DataTable)
'Graphics object
Dim Dep_Graph As Graphics = TargetPanel.CreateGraphics
Dim Offset As Integer = 45
Dim DepName As String = ""
'Graph area
With TargetPanel
GraphHeight = .Height - (Offset + Gap)
GraphWidth = .Width - (2 * Gap)
GraphXOrigin = Gap
GraphYOrigin = (Offset + Gap)
End With
Dim Filter As String = "" 'Filter used for querying the data table
Dim FoundMax() As DataRow 'A data row generated by a filter
Dim FoundRows() As DataRow 'A data row generated by a filter
'The data table has a max value for food sales in the given period
If (TargetPanel.Name.Contains("Food")) Then
Filter = "Department LIKE 'F%' OR Department LIKE 'S%'"
Else
Filter = "Department LIKE 'W%'"
End If
Select Case Report
Case ReportMode.Day
TableGraph.DefaultView.Sort = "Day DESC"
FoundMax = TableGraph.Select(Filter)
MaxDataValue = FoundMax(0).Item("Day")
Case ReportMode.Week
TableGraph.DefaultView.Sort = "Week DESC"
FoundMax = TableGraph.Select(Filter)
MaxDataValue = FoundMax(0).Item("Week")
Case ReportMode.Month
TableGraph.DefaultView.Sort = "Month DESC"
FoundMax = TableGraph.Select(Filter)
MaxDataValue = FoundMax(0).Item("Month")
Case ReportMode.Year
TableGraph.DefaultView.Sort = "Year DESC"
FoundMax = TableGraph.Select(Filter)
MaxDataValue = FoundMax(0).Item("Year")
End Select
TableGraph.DefaultView.Sort = "Department"
'Select only the food department values
If (TargetPanel.Name.Contains("Food")) Then
Filter = "Department LIKE 'F%' OR Department LIKE 'S%'"
Else
Filter = "Department LIKE 'W%'"
End If
FoundRows = TableGraph.Select(Filter)
'Calculate the width of each column
Dim NumberOfColumns As Integer = (FoundRows.GetUpperBound(0) + 1)
ColWidth = (GraphWidth - ((NumberOfColumns) * Gap)) / NumberOfColumns
'Using the graphics object draw the columns
With Dep_Graph
MessageBox.Show("Clearing graph area")
'Using the FoundMax data row extract the Day max value
ClearGraph(TargetPanel)
For Counter As Integer = 0 To FoundRows.GetUpperBound(0)
Select Case Report
Case ReportMode.Day
DataValue = FoundRows(Counter).Item("Day")
DepName = FoundRows(Counter).Item("Department")
If (TargetPanel.Name.Contains("Wine")) Then
ReportLabel(Counter + 12).Text = GetLabelData(DepName, DataValue)
Else
ReportLabel(Counter).Text = GetLabelData(DepName, DataValue)
End If
Case ReportMode.Week
DataValue = FoundRows(Counter).Item("Week")
DepName = FoundRows(Counter).Item("Department")
If (TargetPanel.Name.Contains("Wine")) Then
ReportLabel(Counter + 12).Text = GetLabelData(DepName, DataValue)
Else
ReportLabel(Counter).Text = GetLabelData(DepName, DataValue)
End If
Case ReportMode.Month
DataValue = FoundRows(Counter).Item("Month")
DepName = FoundRows(Counter).Item("Department")
If (TargetPanel.Name.Contains("Wine")) Then
ReportLabel(Counter + 12).Text = GetLabelData(DepName, DataValue)
Else
ReportLabel(Counter).Text = GetLabelData(DepName, DataValue)
End If
Case ReportMode.Year
DataValue = FoundRows(Counter).Item("Year")
DepName = FoundRows(Counter).Item("Department")
If (TargetPanel.Name.Contains("Wine")) Then
ReportLabel(Counter + 12).Text = GetLabelData(DepName, DataValue)
Else
ReportLabel(Counter).Text = GetLabelData(DepName, DataValue)
End If
End Select
If (MaxDataValue > 0) Then
'Set column height to a scale of the maximum value
ColHeight = (DataValue * GraphHeight) / MaxDataValue
End If
'Set colours
PenWWC.Color = Colors(Counter + 2)
BrushWWC = New SolidBrush(Colors(Counter + 2))
'Draw and fill
DrawColumn(Dep_Graph, GraphXOrigin, TargetPanel.Height - ColHeight - Offset, ColWidth, ColHeight, PenWWC, BrushWWC)
'Reset X0 to the next point
GraphXOrigin = GraphXOrigin + ColWidth + Gap
Next
End With
GraphXOrigin = Gap
Dep_Graph.Dispose()
End Sub
As can be seen in the video I have included a message box at the point where I clear the graphing area to show that this is NOT what is happening.
As I say, up until recently the form displayed with graphs showing; no changes have been made to this section of the application code so i don't know what is happening.
Further, as shown in the video, if I select the date for which the form is set, the graphs appear and if I change date, the new graphs appear, without problem.
Any suggestions most welcome. AFAIK I have posted all the relevant code here.
TIA,
Dermot