Unusual Glitch when Opening Forms - vb.net

Question

When I maximise a form in my project and open another form from it (using a button), I'm getting an unusual glitch which I can only explain with the use of the screenshots below.
In this image, I have got an order screen and a freight screen. The order screen is maximised into an MDI screen when I hit the 'Add Freight' button, then upon opening the freight management screen, it is setting both forms to WindowState.Normal, which I'm doing programmatically and I understand why it sets both forms to normal window state, however, as you can, it is leaving a trace of the order screen behind in maximised view.
To explain more clearly, the forms have been changed from WindowState.Maximized to WindowState.Normal, and in the image the form in the top left corner is fine, but the order form is still showing in both normalised and maximised, but the maximised window doesn't exist, it disappears when you move the other screens around.
The strangest thing about this is that I'm using the same code to open other windows in the exact same way elsewhere in the program yet this glitch isn't happening.
There are only 2 "parent" forms which do this when opening other forms from within them.
Has anyone else ever had this issue? What is a way around it? This also happens even if I open the other form in maximised mode, so it's not as simple as just opening it in maximised view.
The code to open the form in the example is the following:
ugProducts.UpdateData()
Try
Dim dt As New DataTable
dt = ugProducts.DataSource
Dim ordnum As Integer
Dim osql As New OleDbCommand
osql.CommandType = CommandType.Text
osql.Connection = con
osql.CommandText = "SELECT [Order_Number] FROM [Order_Freight] WHERE [Order_Reference] = ?"
osql.Parameters.AddWithValue("#onum", lblReference.Text.ToString)
ordnum = Convert.ToInt32(osql.ExecuteScalar)
Dim ORef As String
ORef = lblReference.Text
Dim FNumber As Integer
Dim fsql As New OleDbCommand
fsql.CommandType = CommandType.Text
fsql.Connection = con
fsql.CommandText = "SELECT [Freight_Number] FROM [Order_Freight] WHERE [Order_Reference] = ?"
fsql.Parameters.AddWithValue("#fnum", lblReference.Text.ToString)
FNumber = Convert.ToInt32(fsql.ExecuteScalar)
Dim PC As String
Try
PC = ugProducts.ActiveRow.Cells("Product_Code").Text.ToString
Catch
PC = ugProducts.Rows(0).Cells("Product_Code").Text.ToString
End Try
Dim SC As String
Try
SC = ugProducts.ActiveRow.Cells("Supplier_Code").Text.ToString
Catch
SC = ugProducts.Rows(0).Cells("Supplier_Code").Text.ToString
End Try
Dim f As New frmEditFreight(con, dt, Me, cmbCustCode.Text, ordnum, ORef, FNumber, PC, SC)
f.MdiParent = Me.MdiParent
f.Show()
Catch ex As Exception
errorLog(ex)
End Try
Then, on the form that is loaded, I have this
Me.Location = New Point(0, 0)
Me.WindowState = FormWindowState.Normal
txtTotal.ReadOnly = True
lftable = New DataTable
If isNewOrder = False Then
Try
For Each dc As DataColumn In lineTable.Columns
If dc.ColumnName = "Order_Number" OrElse dc.ColumnName = "Product_Code" OrElse dc.ColumnName = "Supplier_Code" Then
lftable.Columns.Add(New DataColumn(dc.ColumnName, dc.DataType))
End If
Next
Dim product As String = ""
Dim supplier As String = fOrder.cmbSupplier.Text
Dim ds As New DataSet
Dim da As New OleDbDataAdapter("SELECT * FROM [Order_Freight] WHERE [Order_Number] = ?", con)
da.SelectCommand.Parameters.Add("#num", OleDbType.Integer).Value = orderNum
da.Fill(ds)
Dim nDt As New DataTable
nDt = ds.Tables(0).Copy()
For Each row As DataRow In nDt.Rows
product = row.Item("Product_Code")
For Each dr As DataRow In lineTable.Rows
If dr.RowState <> DataRowState.Deleted Then
If dr.Item("Product_Code") = product Then
dr.Delete()
Else
End If
Else
If dr.Item("Product_Code", DataRowVersion.Original) = product Then
dr.Delete()
Else
End If
End If
Next
Next
For Each dr As DataRow In lineTable.Rows
If dr.RowState <> DataRowState.Deleted Then
dr.Item("Order_Number") = orderNum
End If
Next
Me.ugProducts.DataSource = lineTable
For Each dc As UltraGridColumn In ugProducts.DisplayLayout.Bands(0).Columns
Dim cName As String = dc.ToString
Select Case cName
Case "Product_Code"
dc.Hidden = False
Case "Order_Number"
dc.Hidden = False
Case "Supplier_Code"
dc.Hidden = False
Case Else
dc.Hidden = True
End Select
Next
loadAddresses(custCode, con)
dtEstDelivery.Value = Date.Today
ugProducts.DisplayLayout.Bands(0).Override.CellClickAction = CellClickAction.RowSelect
selectedTable.Columns.Add("Product_Code")
selectedTable.Columns.Add("Supplier_Code")
selectedTable.Columns.Add("RowIndex")
freightTable = New DataTable
With freightTable.Columns
.Add("Freight_Number")
.Add("Address_Code")
.Add("Est_Delivery")
.Add("Product_Code")
.Add("Freight_Desc")
.Add("Freight_Val", GetType(Decimal))
.Add("Supplier_Code")
.Add("freeDelivery", GetType(Boolean))
End With
ugFreight.DataSource = freightTable
ugSelected.DataSource = selectedTable
ugSelected.DisplayLayout.Bands(0).Override.CellClickAction = CellClickAction.RowSelect
Catch ex As Exception
errorLog(ex)
End Try
Else
Try
Me.ugProducts.DataSource = lineTable
For Each dc As UltraGridColumn In ugProducts.DisplayLayout.Bands(0).Columns
Dim cName As String = dc.ToString
Select Case cName
Case "Product_Code"
dc.Hidden = False
Case "Product_Description"
dc.Hidden = False
dc.Header.Caption = "Description"
Case "Supplier_Code"
dc.Hidden = False
dc.Header.Caption = "Supplier"
Case Else
dc.Hidden = True
End Select
Next
loadAddresses(custCode, con)
dtEstDelivery.Value = Date.Today
ugProducts.DisplayLayout.Bands(0).Override.CellClickAction = CellClickAction.RowSelect
selectedTable.Columns.Add("Product_Code")
selectedTable.Columns.Add("Supplier_Code")
selectedTable.Columns.Add("RowIndex")
freightTable = New DataTable
With freightTable.Columns
.Add("Freight_Number")
.Add("Address_Code")
.Add("Est_Delivery")
.Add("Product_Code")
.Add("Freight_Desc")
.Add("Freight_Val", GetType(Decimal))
.Add("Supplier_Code")
.Add("freeDelivery", GetType(Boolean))
End With
ugFreight.DataSource = freightTable
ugSelected.DataSource = selectedTable
ugSelected.DisplayLayout.Bands(0).Override.CellClickAction = CellClickAction.RowSelect
Catch ex As Exception
errorLog(ex)
End Try
End If
bLoading = False
Followed by some ordinary stuff, setting DataTables, loading in data, etc.
The other form which is having the issue has this code:
Try
Dim grid As UltraGrid = DirectCast(sender, UltraGrid)
Dim lastElement As UIElement = ugRates.DisplayLayout.UIElement.LastElementEntered
Dim rowElement As RowUIElement
If TypeOf lastElement Is RowUIElement Then
rowElement = DirectCast(lastElement, RowUIElement)
Else
rowElement = DirectCast(lastElement.GetAncestor(GetType(RowUIElement)), RowUIElement)
End If
If rowElement Is Nothing Then Return
Dim row As UltraGridRow = DirectCast(rowElement.GetContext(GetType(UltraGridRow)), UltraGridRow)
If (row Is Nothing) Then Return
Dim MousePosition As Point = grid.PointToClient(Control.MousePosition)
If Not lastElement.AdjustableElementFromPoint(MousePosition) Is Nothing Then Return
Select Case row.Cells("cType").Value
Case "Acquisition Rate"
Dim supplier As String
If rbtnAllSuppliers.Checked = True Then
supplier = row.Cells("Supp_Code").Value
Else
supplier = cmbSupplier.Text
End If
Dim f As New frmCommission(con, row.Cells("Comm_Code").Value, supplier, True)
f.MdiParent = Me.MdiParent
f.Show()
With the rest of the select case below. The form being opened in this case then has the code
Me.Location = New Point(0, 0)
Me.WindowState = FormWindowState.Normal
Me.Cursor = Cursors.Default
isUpdate = False
Me.ugComm.ContextMenuStrip = cmCommRate
With updateDT.Columns
.Add("Apply", GetType(Boolean)).DefaultValue = False
.Add("Product_Code")
.Add("Commission_Rate")
.Add("Multiplier")
End With
btnCustomerSearch.Enabled = False
Try
Dim da As New OleDb.OleDbDataAdapter
Dim ds As New DataSet
sql = "SELECT * FROM [System Settings]"
da = New OleDb.OleDbDataAdapter(sql, con)
Dim dt As New DataTable
da.Fill(dt)
If dt.Rows(0).Item("enableAqDate") = False Then
rbtnAcq.Enabled = False
End If
If cCode <> "" And sCode <> "" Then
cmbSupp.Text = sCode
cmbSupp_ValueChanged(sender, New EventArgs)
End If
disableControls()
cmbSupp.Refresh()
txtCommCode.Refresh()
ugComm.Refresh()
cmbSupp.Enabled = False
isLoad = False
If isEnquiry = True Then
txtCommCode.Text = cCode
loadEnquiry()
ugComm.Enabled = True
cmdAddRange.Enabled = False
cmdUpdateRange.Enabled = True
cmbSupp.Value = sCode
txtCommCode.Text = cCode
End If
Catch ex As Exception
errorLog(ex)
End Try
When trying to insert the code suggested for making dpiaware = True, I've not been able to see anywhere in the code that this would go?

Answer 1

The culprit seems to be setting the WindowState property to Normal inside the Load event of a mdi child form when active mdi child form is maximized.
At this time the target form is in some intermediate state - the event is called as part of the window handle creation, the handle is already created, Visible property is True (but the form is not really shown on screen), WindowState returns Maximized and trying to set it to Normal leads internally to ShowWindow API call.
It's hard to tell where exactly is the bug (there are a lot of internal flags and windows messages handling inside the Form class), but the end effect is that the MDIClient and the currently active mdi child form are not correctly invalidated, hence the visual effect you are experiencing.
With that being said, there are several workarounds:
(1) At the form being shown side:
Move the Me.WindowState = FormWindowState.Normal to the Shown event.
(2) At the caller side:
(A) Add Me.WindowState = FormWindowState.Normal before f.Show()
or
(B) Add Me.MdiParent.Invalidate(True) after f.Show()
or
(C) Add Me.MdiParent.Refresh() after f.Show()
My personal preference would be the option (1) since it encapsulates a logic which is specific to the called form inside that form.