App crashes the first time I select an item in a combobox defined programmatically in a grid that is added as a child of a stack panel - combobox

Question

I get the following error on a Zebra tablet t55 when running my app:
Unhandled exception at 0x00007FFEA4A22D45 (Windows.UI.Xaml.dll) in PerfectDelivery.exe: 0xC000041D: An unhandled exception was encountered during a user callback.
It happens after I load all my sqlite database and run the app the first time. After the crash I start the app back up again and it runs fine. The offending Combobox is here:
private void InitProducts()
{
StpProducts.Children.Clear();
_lstItemsInMultipleCrates = new List<int>();
Invoice deliveryDetails = new Invoice(((App)Application.Current).OrderId);
ItemsInCrate = new List<InvoiceItem>();
if (_selectedCrate != null)
{
btnFinishCrate.Visibility = Visibility.Visible;
foreach (InvoiceItem i in deliveryDetails.InvoiceItems.Where(
x => x.CrateNumber.CrateId == _selectedCrate))
{
ItemsInCrate.Add(i);
GridProducts = new Grid();
GridProducts.Height = 35;
GridProducts.Width = 600;
GridProducts.HorizontalAlignment = HorizontalAlignment.Left;
ColumnDefinition cdProductName = new ColumnDefinition();
cdProductName.Width = new GridLength(170, GridUnitType.Star);
ColumnDefinition cdQty = new ColumnDefinition();
cdQty.Width = new GridLength(45, GridUnitType.Star);
ColumnDefinition cdUnits = new ColumnDefinition();
cdUnits.Width = new GridLength(60, GridUnitType.Star);
ColumnDefinition cdChecked = new ColumnDefinition();
cdChecked.Width = new GridLength(30, GridUnitType.Star);
ColumnDefinition cdDropdown = new ColumnDefinition();
cdDropdown.Width = new GridLength(80, GridUnitType.Star);
ColumnDefinition cdFiller = new ColumnDefinition();
cdFiller.Width = new GridLength(1, GridUnitType.Star);
RowDefinition row = new RowDefinition();
row.Height = new GridLength(35, GridUnitType.Star);
GridProducts.ColumnDefinitions.Add(cdProductName);
GridProducts.ColumnDefinitions.Add(cdQty);
GridProducts.ColumnDefinitions.Add(cdUnits);
GridProducts.ColumnDefinitions.Add(cdChecked);
GridProducts.ColumnDefinitions.Add(cdDropdown);
TextBlock txbOrderDetailPickedId = new TextBlock { Name = "ODPID" };
txbOrderDetailPickedId.Text = i.OrderDetailPickedId.ToString("G");
txbOrderDetailPickedId.Visibility = Visibility.Collapsed;
TextBlock txbOriginalQty = new TextBlock { Name = "OQ" };
txbOriginalQty.Text = i.Quantity.ToString("N");
txbOriginalQty.Visibility = Visibility.Collapsed;
List<long?> lstCrateCount = new List<long?>();
foreach (InvoiceItem crateCount in deliveryDetails.InvoiceItems.Where(x => x.CrateNumber.OrderDetailPickedId == i.OrderDetailPickedId))
{
lstCrateCount.Add(crateCount.CrateNumber.CrateId);
}// return count of crates for item. If > 1 display crate number(s)
TextBlock txbProductName = new TextBlock();
TextBox txbQuantity = new TextBox();
txbQuantity.Text = i.Quantity.ToString("N");
txbQuantity.Height = 35;
InputScope scope = new InputScope();
InputScopeName scopeName = new InputScopeName { NameValue = InputScopeNameValue.Number };
scope.Names.Add(scopeName);
txbQuantity.InputScope = scope;
TextBlock txbUnits = new TextBlock();
txbUnits.Text = i.PackDescription;
txbUnits.HorizontalTextAlignment = TextAlignment.Center;
txbUnits.VerticalAlignment = VerticalAlignment.Center;
CheckBox chkChecked = new CheckBox();
---> CmbDiscrepancies = new ComboBox{ SelectedIndex = -1};
if (CmbDiscrepancies?.Items != null)
{
CmbDiscrepancies.Items.Add("Correct");
CmbDiscrepancies.Items.Add("Damaged");
CmbDiscrepancies.Items.Add("Missing");
CmbDiscrepancies.Items.Add("Wrong Item");
CmbDiscrepancies.Items.Add("Out of Stock");
CmbDiscrepancies.Items.Add("Incorrect Amt");
}
CmbDiscrepancies.SelectedIndex = 0;
CmbDiscrepancies.VerticalAlignment = VerticalAlignment.Center;*
if (lstCrateCount.Count == 1)
{
txbProductName.Text = i.ProductName;
}
else if (!Crate.ItemInMultipleCrates(i.OrderDetailPickedId))
{
_lstItemsInMultipleCrates.Add(i.OrderDetailPickedId);
txbProductName.TextWrapping = TextWrapping.Wrap;
txbProductName.Text = i.ProductName + "\r\n" + "(";
int count = 0;
foreach (long? crate in lstCrateCount)
{
count++;
txbProductName.Text += count != lstCrateCount.Count ? crate + ", " : crate + ")\r\nQty is the total in all crates listed above.";
}
GridProducts.Height = 50 * (lstCrateCount.Count * .66);
row.Height = new GridLength(GridProducts.Height, GridUnitType.Pixel);
}
if (Crate.ItemInMultipleCrates(i.OrderDetailPickedId))
{
txbProductName.Foreground = new SolidColorBrush(Color.FromArgb(255, 255, 0, 0));
CmbDiscrepancies.IsEnabled = false;
txbQuantity.IsEnabled = false;
if (_lstItemsInMultipleCrates.Count > 0)
GridProducts.Height = 35 * (_lstItemsInMultipleCrates.Count * 1.32);
else
{
GridProducts.Height = 35 * 1.32;
}
row.Height = new GridLength(GridProducts.Height, GridUnitType.Pixel);
txbProductName.Text = i.ProductName + "\r\n" + "(Item is in multiple crates)";
chkChecked.IsChecked = true;
chkChecked.IsEnabled = false;
}
GridProducts.Children.Add(txbOriginalQty);
GridProducts.Children.Add(txbOrderDetailPickedId);
GridProducts.Children.Add(txbProductName);
GridProducts.Children.Add(txbQuantity);
GridProducts.Children.Add(txbUnits);
GridProducts.Children.Add(chkChecked);
GridProducts.Children.Add(CmbDiscrepancies);
Grid.SetColumn(txbProductName, 0);
Grid.SetColumn(txbQuantity, 1);
Grid.SetColumn(txbUnits, 2);
Grid.SetColumn(chkChecked, 3);
Grid.SetColumn(CmbDiscrepancies, 4);
Grid.SetRow(txbProductName, 0);
Grid.SetRow(txbQuantity, 0);
Grid.SetRow(txbUnits, 0);
Grid.SetRow(chkChecked, 0);
Grid.SetRow(CmbDiscrepancies, 0);
GridProducts.RowDefinitions.Add(row);
StpProducts.Children.Add(GridProducts);
}
}
The XAML is
<ScrollViewer x:Name="ScvProducts" HorizontalAlignment="Left" Height="354" Margin="375,146,0,0" VerticalAlignment="Top" Width="638" BorderBrush="#FF1B933C" BorderThickness="2" >
<StackPanel x:Name="StpProducts" MinHeight="450" Width="612" HorizontalAlignment="Left" VerticalAlignment="Top" Orientation="Vertical" Height="995" >
<Grid x:Name="GridProducts">
<ComboBox x:Name="CmbDiscrepancies" Visibility></ComboBox>
</Grid>
</StackPanel>
</ScrollViewer>

Answer 1

Upgrading from Windows 10 1709 to 1803 fixed the existing code. I also got rid of the stack panel and add the row definitions dynamically which seems to have addressed the 1709 version.