Develop Reference

list picker gives error when selting selected item

I have a listpicker control that has a list of meals. This control is populated using following code where viewModelMeal returns a collection of type Meal
After that I get the Diet data from database and that also has a column name MealId. Now when I try to set the selected item of listpicker control with that mealid it gives me error that "SelectedItem must always be set to a valid value". Here is the function setting the selected item of listpicker
and XAML code
<toolkit:ListPicker Name="lpMeal" Height="60" ItemsSource="{Binding}" VerticalAlignment="Bottom" Background="Black" FullModeHeader="Select your Meal" Foreground="White" ExpansionMode="FullScreenOnly" Margin="5,0">
<toolkit:ListPicker.ItemTemplate>
<DataTemplate>
<StackPanel Name="listpickerStackpannel" >
<!--<TextBlock Text="{Binding mealId}" Visibility="Collapsed"></TextBlock>-->
<TextBlock Text="{Binding mealName}" TextAlignment="Center" FontFamily="Times New Roman" FontSize="30"></TextBlock>
</StackPanel>
</DataTemplate>
</toolkit:ListPicker.ItemTemplate>
<toolkit:ListPicker.FullModeItemTemplate>
<DataTemplate>
<StackPanel Name="listpickerStackpannel" Margin="10">
<!--<TextBlock Text="{Binding mealId}" Visibility="Collapsed"></TextBlock>-->
<TextBlock Text="{Binding mealName}" TextAlignment="Center" FontFamily="Times New Roman" FontSize="30"></TextBlock>
</StackPanel>
</DataTemplate>
</toolkit:ListPicker.FullModeItemTemplate>
</toolkit:ListPicker>

To elaborate on Chubosaurus Software's comment.
You need to set the SelectedItem to a value that is in the list that the lpMeal ItemsSource is bound to. In your case:
lpMeal.SelectedItem = DietViewModel.GetDefault().GetItem(ID);
Therefore you are setting the SelectedItem to a member of the list in it's ItemsSource.

How to Save to Database from ListBox?

I know how to save to my database from a datagrid's selected row, but I want to save all records from my list box to the database. Here is the related xaml for the ListBox:
<UserControl.Resources>
<DataTemplate x:Key="EventDataTemplate">
<StackPanel Name="OuterStackPanel">
<TextBox Text="{Binding Title}" Name="TextBoxTitle"/>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding BeginDate}" Name="TextBoxBeginDate"/>
<TextBlock Text=" - "/>
<TextBlock Text="{Binding EndDate}" Name="TextBoxEndDate"/>
</StackPanel>
<TextBox Text="{Binding Venue}" Name="TextBoxVenue"/>
<TextBox Text="{Binding Location}" Name="TextBoxLocation"/>
<TextBlock Name="TextBlockID" Text="{Binding id}"/>
</StackPanel>
</DataTemplate>
</UserControl.Resources>
<ListBox x:Name="AllEventsListBox" ItemTemplate="{StaticResource EventDataTemplate}"/>
With my DataGrid method, I use this codebehind to save its row's related TextBoxes to the database:
MyServiceClient client = new MyServiceClient();
client.UpdateEventCompleted += new EventHandler<UpdateEventCompletedEventArgs>(client_UpdateEventCompleted);
singleEvent.id = int.Parse(LblID.Content.ToString());
singleEvent.Title = TextBoxTitle.Text;
singleEvent.Location = TextBoxLocation.Text;
singleEvent.BeginDate = TextBoxBegin.Text;
singleEvent.EndDate= TextBoxEnd.Text;
singleEvent.Venue = TextBoxVenue.Text;
client.UpdateEventAsync(singleEvent);
However, I would like to save all of the altered text from my generated ListBoxItems, instead of just one row at a time from my DataGrid method.
Is this possible?

c# find texbox in WinPhone7 silverlight app

I have something like this:
<ListBox Height="456" Margin="30,113,0,0" x:Name="listBox1" Width="446" Background="Black">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28" Orientation="Horizontal">
<TextBlock Text="{Binding name}" FontSize="28" Padding="10" >
<toolkit:GestureService.GestureListener>
<toolkit:GestureListener
Hold="GestureListenerHold" />
</toolkit:GestureService.GestureListener>
</TextBlock>
<TextBlock Text="{Binding id}" FontSize="24" Padding="10" >
<toolkit:GestureService.GestureListener>
<toolkit:GestureListener
Hold="GestureListenerHold" />
</toolkit:GestureService.GestureListener>
</TextBlock>
<TextBlock Text="{Binding status}" FontSize="24" Padding="10">
<toolkit:GestureService.GestureListener>
<toolkit:GestureListener
Hold="GestureListenerHold" />
</toolkit:GestureService.GestureListener>
</TextBlock>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
and in my app i do:
data = (List<Device>)serializer.Deserialize(stream);
this.listBox1.ItemsSource = data;
on every textblock I have a gesture listener which should provide the user with the option to change 'name', so when they hold the textblock the app navigates him to another page where he fills in the form.
My question is how to find the texblock which is binding 'name' when I click and hold another texblock?

You could use Linq-to-VisualTree, a utility which I wrote which allows you to navigate the visual tree:
http://www.scottlogic.co.uk/blog/colin/2010/03/linq-to-visual-tree/
Firstly, name the TextBlock so that it can be uniquely identified:
<TextBlock x:Name="NameText" Text="{Binding name}" FontSize="28" Padding="10" />
Then, when one of your other TextBlocks is tapped, you can find it as follows:
// locate the parent stackpanel
var parentStackPanel = tappedTextBlock.Ancestors().First()
// locate the names TextBlock
var nameTextBlock = parentStackPanel.Elements()
.Where(el => el.Name == "NameText").Single();

Cast the sender in the GestureListenerHold method.

Accessing a TextBlock which is contained inside a ListBox

I have a textblock which is inside a listbox and I am trying to write an if statement which is dependant on the contents of this textblock. I am trying to get the data from the TextBlack which I have named "category1" however when I try to write my if statement I am getting a message which just says
"the name category1 does not exist in the current context"
I tired moving that TextBLock out of the ListBox and it works fine but wont work while its inside there. Does anyone know how to reference this textblock.
Here is the my XAML code
<ListBox x:Name="HINList" Margin="0,300,-12,0" ItemsSource="{Binding Details}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Margin="0,0,0,17" Width="432">
<TextBlock Text="{Binding HINNumber}" TextWrapping="Wrap" Margin="12,-6,12,0" Style="{StaticResource PhoneTextExtraLargeStyle}"/>
<TextBlock Text="{Binding CategoryLetter}" TextWrapping="Wrap" Margin="12,-6,12,0" Style="{StaticResource PhoneTextNormalStyle}"/>
<TextBlock x:Name="category1" Text="{Binding Category1}" TextWrapping="Wrap" Margin="12,-6,12,0" Style="{StaticResource PhoneTextNormalStyle}"/>
<TextBlock Text="{Binding Category2}" TextWrapping="Wrap" Margin="12,-6,12,0" Style="{StaticResource PhoneTextNormalStyle}"/>
<TextBlock Text="{Binding Category3}" TextWrapping="Wrap" Margin="12,-6,12,0" Style="{StaticResource PhoneTextNormalStyle}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>

Assuming you're writing your if statement in the code behind file, wouldn't something like:
if(((WhateverTypeIsInDetailsCollection)HINList.SelectedItem).Category1 == something) {
// then do whatever you want
}
As Russell pointed out there is a category1 item for every entry in the list. I assume you wanted to do something with the selected item.

This is due to xaml namescopes. The names inside a DataTemplate are in a different namescope than outside, that's why you can't access them (what #Russell pointed is part of why it's done this way).
I think that you want to access that field for the "Category1" property on the selected item of the HINList ListBox that is bound to the Details collection. What you can do is set the binding on the Category1 to be two way, and bind the SelectedItem of the ListBox to a Detail item like so:
xaml:
<ListBox x:Name="HINList" ItemsSource="{Binding Details}"
SelectedItem={Binding SelectedDetailItem, Mode=TwoWay}>
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Margin="0,0,0,17" Width="432">
<TextBlock Text="{Binding Category1, Mode=TwoWay}" TextWrapping="Wrap" .../>
<!-- the other fields -->
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
code-behind
if(SelectedDetailsItem.Category1==...)
{
....
}
Hope this helps :)

How to change datatemplate through code

I have ListBox and DataTemplate
I need Set GroupBox Heigth = 300
How to do it?
<DataTemplate x:Key="data_template">
<GroupBox Header="Категория" Width="300" HorizontalAlignment="Stretch" x:Name="GroupBox">
<DockPanel Tag="{Binding id}">
<Button Click="Button_Click" DockPanel.Dock="Top" >
<Button.Content>
<DockPanel>
<TextBlock Text="{Binding title}" TextWrapping="Wrap" DockPanel.Dock="Top" Padding="5" HorizontalAlignment="Center" Foreground="#FFB51414" />
<l:ScrollViewerEx VerticalScrollBarVisibility="Auto" >
<TextBlock Text="{Binding description}" DockPanel.Dock="Top" TextWrapping="Wrap" Padding="5" IsHitTestVisible="False" />
</l:ScrollViewerEx>
</DockPanel>
</Button.Content>
</Button>
</DockPanel>
</GroupBox>
</DataTemplate>

In case, someone tried to resolve my previous question, I did it like the following:
DataTemplate mycolumnDataTemplate = null;
var dataTemplateStream = new SomeClass().GetType().Assembly.GetManifestResourceStream("Some.Namespace.SomeReosurceName.xaml");
string dataTemplateString = new System.IO.StreamReader(dataTemplateStream).ReadToEnd();
dataTemplateString = dataTemplateString.Replace("[0]", browserColumn.ColumnName);
mycolumnDataTemplate = XamlReader.Load(dataTemplateString) as DataTemplate;

What are you trying to achieve? Do you want the GroupBox Height to be changed at the runtime of your application, when some event occurred or some data has changed? If so, then what you are probably looking for is a data trigger or event trigger, which you simply need to add to your DataTemplate.