VB.NET Form.Show closes the application for unknown reason - vb.net

Question

VB.NET Framework 4.7.2
Visual Studio Community 2019 V16.11.2
I have a WinForms application and, for the most part, I start with a form to display the loading of datatables. This is handled in the Application Events module:
Private Sub MyApplication_Startup(sender As Object, e As StartupEventArgs) Handles Me.Startup
If String.IsNullOrEmpty(My.Settings.TheCompany) Then
MainForm = FormConnection
Else
MainForm = FormDataLoad
End If
End Sub
When the datatables are all loaded the FormDataLoad has a close button which is enabled by the procedure which loads all the datatables:
With FormDataLoad
.ButtonClose.Visible = True
End With
When the button is pressed it calls another form which displays various charts etc based on the datatables which have been loaded:
Private Sub ButtonClose_Click(sender As Object, e As EventArgs) Handles ButtonClose.Click
Me.Close()
End Sub
Private Sub FormDataLoad_FormClosed(sender As Object, e As FormClosedEventArgs) Handles Me.FormClosed
With FormOverview
.Show()
End With
End Sub
When FormOverview loads, its labels, charts etc are all initialised and drawn BUT, mysteriously, the form closes and the application ends. The Application Shutdown event is raised:
' Shutdown: Raised after all application forms are closed. This event is not raised if the application terminates abnormally.
Private Sub MyApplication_Shutdown(sender As Object, e As EventArgs) Handles Me.Shutdown
MessageBox.Show("Closing the application for some unknown reason")
End Sub
When this message box is displayed it means that the application has closed but not as a result of any unhandled exception. Nowhere in the project is there any code to call FormOverview.close so I am at a loss to understand what is happening.
The form load code is here:
Private Sub FormOverview_Load(sender As Object, e As EventArgs) Handles Me.Load
With Me
'Set the form caption and back colour and font
.Text = "Retail Management Hero Data Visualisation Overview"
.BackColor = Color.GhostWhite
.Font = U.BasicFontSmall
'Add event handler for the DAL
AddHandler D.ConnectionOpened, AddressOf Connected
'Form level variables for the KPJs
Dim ITO As String = ""
Dim ATV As String = ""
Dim CRR As String = ""
Dim GMROI As String = ""
Dim OOS As String = ""
Dim StocksSales As String = ""
With KPIData.Rows(0)
Me.Text = My.Settings.TheCompany & " " & Me.Text
ITO = .Item("ITO").ToString
CRR = .Item("CRR").ToString
ATV = "€" & .Item("ATV").ToString
GMROI = "€" & .Item("GMROI").ToString
OOS = .Item("OOSRatio").ToString
StocksSales = .Item("StocksToSales").ToString
End With
For Each CTL As Control In .Controls
If TypeOf CTL Is Label Then
With CTL
If .Name.Contains("Value") Then
.Font = U.BasicFontSuperLarge
.BackColor = Color.Yellow
Else
.BackColor = U.Spurs
.ForeColor = Color.GhostWhite
End If
End With
End If
Next
With .LabelReportDate
.Text = "Reports As Of " & ReportDate
End With
With .LabelATVValue
.Text = U.DecimalToSuperSubFormat(ATV, True)
End With
With .LabelGMROIValue
.Text = U.DecimalToSuperSubFormat(GMROI, True)
End With
With .LabelCRRValue
.Text = U.DecimalToSuperSubFormat(CRR, True) & "%"
End With
With .LabelITOValue
.Text = U.DecimalToSuperSubFormat(ITO, True)
End With
With .LabelOOSValue
.Text = U.DecimalToSuperSubFormat(OOS, True) & "%"
End With
With .LabelStocksSalesValue
.Text = U.DecimalToSuperSubFormat(StocksSales, True) & "%"
End With
'Extract the names of the X and Y axes
Dim Xname As String = ""
Dim Yname As String = ""
With WineData
Xname = .Columns("Department").ColumnName
Yname = .Columns("Day").ColumnName
End With
'Draw the charts
DrawColumnChart(WineData, .ChartWine, "Wine sales", Xname, Yname, 250, False)
DrawColumnChart(OtherData, .ChartNonWine, "Other sales", Xname, Yname, 25, False)
'Centre on the screen
.CenterToScreen()
End With
End Sub
So, what should happen is that this form displays centre screen with charts etc all displayed correctly.
If anyone has any ideas I would be most grateful.
Dermot

Answer 1

I found out what was causing the problem.
In the Project's properties, in the Application tab, there Combo selector, Shutdown mode.
The option I had selected was When startup form closes - by changing this to When last form closes the issue went away.
Like many problems, when you look at it too long you can't see the woods for the trees.