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selected value cannot be set

I have a combobox which gets its Items from some scan function.
If the user select an element, in the next time, the user's chosen item should be selected (if it is present on the scan function output). The problem is that I cannot select it.
Here is the declaration of the ComboBox:
<ComboBox Grid.Column="1" Grid.Row="0" Margin="5" Name="SerialPortNames" Text="{Binding Name}" IsEditable="False"/>
and here what I have tried so far:
private void Window_Loaded(object sender, RoutedEventArgs e)
{
string portNameSetting = Settings.Default["SerialPortName"].ToString();
SerialPortNames.ItemsSource = SerialPort.GetPortNames();
foreach (string SerialPortNameItem in SerialPortNames.Items)
{
if (SerialPortNameItem == portNameSetting)
{
SerialPortNames.Text = SerialPortNameItem; // why this is not working
break;
}
}
}
by debugging this, I get the item selected in the combobox, but it seems that something override it and it is empty!

In your code you Binded the Text propery and also setting it from code behind
Remove Text="{Binding Name}" from the combobox
<ComboBox Width="200" Height="200" Grid.Column="1" Grid.Row="0" Margin="5" Name="SerialPortNames" IsEditable="False"/>

Reach a TextBlock from a specific ListViewItem from the ListView in Windows Phone 8.1 XAML programmatically

I am a new developer on Windows Phone 8.1, I am try to reach a specific ListView item from the ListView collection and be able to color it or color the TextBock inside of it, But I can't reach the item or reach any of items inside of ListView, Please take a look for my below code :
protected async override void OnNavigatedTo(NavigationEventArgs e)
{
SQLiteRT db1 = new SQLiteRT();
var db_connection = await db1.Connection("MyDB.sqlite");
List<MyTBL> t_list = db1.GetTable("SELECT * FROM MyTBL LIMIT 4 ORDER BY RANDOM() ;");
db_connection.Close();
LV_Options.ItemsSource = t_list;
}
// my List View called LV_Options
private void LV_Options_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
ListView lv1 = sender as ListView;
if (lv1 == null)
return;
MyTBL wrd = lv1.SelectedItem as MyTBL;
if (wrd == null)
return;
TextBlock tb = lv1.FindName("TB_AMean1") as TextBlock;
tb.FontSize = 17; // here I got debug error (it not worked !!!!!!!)
var item = LV_Options.Items.ElementAt(3); // this seems not work also !!!!
item.BackColor = Color.LightSteelBlue;
}
As you can see above, I tried to reach a specific item by LV_Options.Items.ElementAt(3) but it doesn't work! I also tried to reach the TextBlock from the selected List view item, but also not worked !
(Updated)
XAML code :
<!-- Title Panel -->
<StackPanel Grid.Row="0" Margin="19,0,0,0">
<TextBlock Name="TB_Rslt" Text="Here result of your answer" Style="{ThemeResource TitleTextBlockStyle}" Margin="0,12,0,0"/>
<TextBlock Text="page title" Margin="0,-6.5,0,26.5" Style="{ThemeResource HeaderTextBlockStyle}" CharacterSpacing="{ThemeResource PivotHeaderItemCharacterSpacing}"/>
</StackPanel>
<!--TODO: Content should be placed within the following grid-->
<Grid Grid.Row="1" x:Name="ContentRoot" Margin="19,10,19,15">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TextBlock Name="TB_Question" Text="Choose Answer " Margin="0,0,25,0" HorizontalAlignment="Right" FontWeight="Bold" FontSize="22" FontFamily="Verdana" RenderTransformOrigin="0.5,0.5" />
<TextBlock Name="TB_EnWord" Text="" Margin="90,0,15,0" HorizontalAlignment="Left" FontWeight="Bold" FontSize="22" FontFamily="Verdana" RenderTransformOrigin="0.5,0.5" TextAlignment="Right" />
<StackPanel Grid.Row="1" Margin="5,22,0,0">
<ListView Name="LV_Options" SelectionChanged="LV_Options_SelectionChanged">
<ListView.ItemTemplate>
<DataTemplate>
<Grid Margin="6">
<StackPanel VerticalAlignment="Top" Margin="10,0,0,0">
<TextBlock Name="TB_AMean1" Text="{Binding AMean1}" TextWrapping="Wrap"/>
</StackPanel>
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</StackPanel>
<Button Name="Btn_Answer" Content="Ansewr" HorizontalAlignment="Left" Grid.Row="1" VerticalAlignment="Bottom" Click="Btn_Answer_Click"/>
My application is a quiz application that offer 4 choices/options as answers for each question, and when user select a true answer, I want to highlight the true answer(true choice) by make its background to green, and if the user selected wrong answer/option I want to make the background of that answer (a specific List View item) with red.
Any help please ?

You're not going to be able to access an element inside a data template like that. Instead, leverage the binding to a view model to set the color and other view-related properties. First, create a wrapper view model for your data class:
public class MyTBLViewModel : INotifyPropertyChanged
{
public MyTBL Entity
{
get { return _entity; }
}
private readonly MyTBL _entity;
public Brush Highlight
{
get { return _brush; }
set
{
_brush = value;
RaisePropertyChanged("Highlight");
}
}
private Brush _highlight;
public double ItemFontSize
{
get { return _itemFontSize; }
set
{
_itemFontSize = value;
RaisePropertyChanged("ItemFontSize");
}
}
private Brush _itemFontSize;
public MyTBLViewModel(MyTBL entity)
{
_entity = entity;
_highlight = new SolidColorBrush(Colors.Transparent);
_itemFontSize = 12;
}
public event PropertyChangedEventArgs PropertyChanged;
protected void RaisePropertyChanged(string propName)
{
var handler = PropertyChanged;
if (handler != null)
handler(this, new PropertyChangedEventArgs(propName));
}
}
Use this as your ItemsSource:
List<MyTBLViewModel> t_list = db1.GetTable("SELECT * FROM MyTBL LIMIT 4 ORDER BY RANDOM() ;")
.AsEnumerable().Select(entity => new MyTBLViewModel(entity)).ToList();
Now in your view, bind the view elements to "Highlight" and "ItemFontSize", and to any other properties you like:
<ListView.ItemTemplate>
<DataTemplate>
<Grid Margin="6" Background="{Binding Highlight}">
<StackPanel VerticalAlignment="Top" Margin="10,0,0,0">
<TextBlock Name="TB_AMean1" Text="{Binding Entity.AMean1}" TextWrapping="Wrap"
FontSize="{Binding ItemFontSize}"/>
</StackPanel>
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
Finally, you can get the data item from the SelectionChangedEventArgs -- use it to update your view-related properties:
private void LV_Options_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
foreach (var item in e.AddedItems.OfType<MyTBLViewModel>())
{
item.Highlight = new SolidColorBrush(Color.LightSteelBlue);
item.ItemFontSize = 17;
}
foreach (var item in e.RemovedItems.OfType<MyTBLViewModel>())
{
item.Highlight = new SolidColorBrush(Colors.Transparent);
item.ItemFontSize = 12;
}
}

var item = LV_Options.Items.ElementAt(3);
This line is incorrect. It will not return you a TextBlock. I don't know what a .BackColor is, and it should not compile. The Items property in a ListView will return you a list of ListViewItems. If you want to access the inside element from a ListViewItem, you'll need to access the ContentTemplateRoot property.
Do not use var ever. It lets you assume that you know the type, whereas if you explicitly typed the declaration you would realize you're doing it wrong.
MyTBL wrd = lv1.SelectedItem as MyTBL;
if (wrd == null)
return;
TextBlock tb = lv1.FindName("TB_AMean1") as TextBlock;
What is a MyTBL type? FindName is only available to framework DependencyObjects so I'm assuming it's a user control? You have to provide a lot more code to show us what you're doing and what you're setting the ListView's ItemsSource and ItemTemplate with and what these errors are and how you have 2 breaking debug errors at once and what the error messages are.
Comprehending runtime error messages is a huge part of being a good developer.

WPF: multiple foreground colors in a ComboBox

In XAML we can set specific properties for each item in a ComboBox, for example:
<ComboBoxItem Foreground="Blue" Background="AntiqueWhite" Content="First Item"/>
<ComboBoxItem Foreground="Yellow" Background="Red" Content="Second Item"/>
When I try to do this when I'm dynamically filling a ComboBox from code, the ComboBox .Foreground property sets a foreground value on all the items. I would like to know if there's anyway to achieve this (setting different foreground colors for different items) in the code.
For example:
ComboBox1[First Item].Foreground = Brushes.Red;
ComboBox1[Second Item].Foreground = Brushes.Blue;

Try to cast ComboBox's Item to ComboBoxItem type, then set it's Foreground property instead of the whole ComboBox's Foreground :
((ComboBoxItem)ComboBox1.Items[0]).Foreground = Brushes.Red;
UPDATE :
if you add new item to ComboBox1 from code this way :
ComboBox1.Items.Add(new ComboBoxItem {Content = "Third Item"});
casting will work fine, because the code above resemble it's XAML counterpart you showed in question. But if you did it this way instead :
ComboBox1.Items.Add("Third Item");
casting won't work. Because that code added string to ComboBox Item instead of ComboBoxItem object. In this case getting ComboBoxItem is not as straightforward, you'll need to get it using ItemContainerGenerator as follow :
var comboBoxItem = (ComboBoxItem)ComboBox1.ItemContainerGenerator.ContainerFromItem(ComboBox1.Items[0]);
comboBoxItem.Foreground = Brushes.Red;

Try this:
XAML
<Grid>
<ComboBox Name="TestComboBox"
Width="100"
Height="30"
Loaded="TestComboBox_Loaded">
<ComboBoxItem Content="First Item"/>
<ComboBoxItem Content="Second Item"/>
</ComboBox>
</Grid>
Code-behind
private void TestComboBox_Loaded(object sender, RoutedEventArgs e)
{
var comboBox = sender as ComboBox;
if (comboBox != null)
{
var firstItem = comboBox.Items[0] as ComboBoxItem;
var secondItem = comboBox.Items[1] as ComboBoxItem;
if (firstItem != null && secondItem != null)
{
firstItem.Foreground = Brushes.Red;
secondItem.Foreground = Brushes.Blue;
}
}
}

Enumerate over each item of listbox to compare internal element values

I have a listbox with a data template bound to a list<class> in the program.
<DataTemplate x:Key="pTemplate">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Ref}" Padding="5,0,0,0"/>
<StackPanel Name="taggedA" Tag="{Binding A}" Orientation="Horizontal">
<TextBlock Name="selectedA" Text="{B}" />
</StackPanel>
<Image Name="ind" Width="40" Height="40" />
</StackPanel>
</DataTemplate>
On button click, I want to go over all the elments of the listbox and check if the stackPanel taggedA's tag == textblock selectedA's text.
This is to be done for each of the items in the list box and the data template is as above. How can this be done?

Easier to compare the binding source directly:
ListBox l = myListBox;
for (int i = 0; i < l.Items.Count; i++)
{
var boundObject = (MyClass)l.Items[i];
MessageBox.Show("They are equal? " + (boundObject.A == boundObject.B));
}

I would agree with #dbaseman. But if you are set on doing it you could do the following:
private void button_click(object sender, RoutedEvent e)
{
foreach(var item in MyListBox.Items)
{
ListBoxItem lbi = MyListBox.ItemContainerGenerator.ContainerFromItem(item);
StackPanel taggedApanel = (lbi.Content as StackPanel).Children[1];
//Do whatever you need to do here
}
}

Get selected item from a ListBox at hold

I've got a ListBox in a WP7 App where I want to do something with an item when the user hold it. The event work's great. My hold method gets called, but I can't detect which element in the list was hold.
ListBox.SelectedItem is always -1 and a code from another post on stackoverflow doens't work:
FrameWorkelement element = (FrameworkElement) e.OriginalSource;
ItemViewModel item = (ItemViewModel) element.DataContext;
I get an InvalidCastException when running it in the second line.

The following code should work.
private void StackPanel_Hold(object sender, GestureEventArgs e)
{
ItemViewModel itemViewModel = (sender as StackPanel).DataContext as ItemViewModel;
string t = itemViewModel.LineOne;
}
Note: before using the DataContext of the sender object, make sure you cast the sender object to the correct class. In this example I use a StackPanel in my DataTemplate:
<ListBox x:Name="MainListBox" Margin="0,0,-12,0" ItemsSource="{Binding Items}" >
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Margin="0,0,0,17" Height="78" Hold="StackPanel_Hold">
<TextBlock Text="{Binding LineOne}" />
<TextBlock Text="{Binding LineTwo}" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>