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Question

I created a textblock on a XAML form within a ContentControl. When I try to program it, C# doesn't recognize the name and I can't do anything with it.

I tried adding a textblock to the form outside of the Content Control, but that still didn't fix the problem.

Here is the XAML code:

<ContentControl>
        <ContentControl.Template>
            <ControlTemplate>
                <Grid VerticalAlignment="Bottom" Height="250" Margin="0,450,0,0">
                    <Rectangle Fill="Beige" Stroke="Black" StrokeThickness="3"
                               Width="639" Height="250" Margin="0,0,0,0"/>
                    <TextBlock Text="Goal:" FontSize="18" Margin="7,50,0,0"/>
                    <TextBlock Text="Eaten:" FontSize="18" Margin="7,120,0,0"/>
                    <TextBlock Text="Remaining:" FontSize="18" Margin="7,190,0,0"/>

                    <TextBlock Text="Calories:" FontSize="18" Margin="140,10,0,0"/>
                    <TextBlock Text="Fat(g):" FontSize="18" Margin="270,10,0,0"/>
                    <TextBlock Text="Carbs(g):" FontSize="18" Margin="380,10,0,0"/>
                    <TextBlock Text="Protein(g):" FontSize="18" Margin="520,10,0,0"/>

                    <TextBlock x:Name="lblCalorieGoal" Text="Peb"
                               TextAlignment="Center" FontSize="18" Margin="-290,50,0,0"/>
                </Grid>
            </ControlTemplate>
        </ContentControl.Template>

    <TextBlock Text="TextBlock" TextWrapping="Wrap"/>
</ContentControl>

And then here is the corresponding working C# code:

public LogFood()
{
    this.InitializeComponent();
    Windows.Storage.ApplicationDataContainer localSettings = 
          Windows.Storage.ApplicationData.Current.LocalSettings;
    Windows.Storage.StorageFolder localFolder = 
          Windows.Storage.ApplicationData.Current.LocalFolder;

    Windows.Storage.ApplicationDataCompositeValue composite =
       (Windows.Storage.ApplicationDataCompositeValue)localSettings
             .Values["nutritionSettings"];

    int calorieMin = Convert.ToInt32(composite["calorieMin"]);
    int calorieMax = Convert.ToInt32(composite["calorieMax"]);
    int gramsFatMin = Convert.ToInt32(composite["gramsFatMin"]);
    int gramsFatMax = Convert.ToInt32(composite["gramsFatMax"]);
    int gramsCarbsMin = Convert.ToInt32(composite["gramsCarbsMin"]);
    int gramsCarbsMax = Convert.ToInt32(composite["gramsCarbsMax"]);
    int gramsProteinMin = Convert.ToInt32(composite["gramsProteinMin"]);
    int gramsProteinMax = Convert.ToInt32(composite["gramsProteinMax"]);

    lblCalorieGoal.Text = calorieMin;
}

I expect to be able to change the text of the textblock. Instead, I get the error, "The name lblCalorieGoal.Text does not exist in the current context."

Answer 1

The key realization here is that a template is potentially a reusable part of XAML, so anything inside is in fact embedded in it a not "publicly" accessible, as there could potentially be multiple instances of the same template materialized on the view.

That being said, you can still access the materialized children inside the template indirectly by searching for them within the template using VisualTreeHelper -

internal static FrameworkElement FindChildByName(DependencyObject startNode, string name)
{
    int count = VisualTreeHelper.GetChildrenCount(startNode);
    for (int i = 0; i < count; i++)
    {
        DependencyObject current = VisualTreeHelper.GetChild(startNode, i);

        if (current is FrameworkElement frameworkElement)
        {
            if (frameworkElement.Name == name)
                return frameworkElement;
        }
        var result = FindChildByName(current, name);
        if ( result != null)
        {
            return result;
        }
    }
    return null;
}

Note, that this works only after the control has loaded (for example in the Page.Loaded event handler -

private void MainPage_Loaded(object sender, RoutedEventArgs e)
{
    var block = FindChildByName(ContentRoot, "lblCalorieGoal") as TextBlock;
}

However, this all is not an ideal solution to your problem. Instead, you should either ditch the use of ContentControl altogether and have the controls in the template directly on the page (which would make them directly accessible from the code-behind), or/and use data-binding to bind data directly to appropriate controls. In this case, I would create a class to hold the data, for example:

public class NutritionInfo
{
    public string CalorieGoal { get; set; }
}

Now instead of ContentControl.ControlTemplate (which replaces the template of the whole control), you will replace the ContentTemplate instead (which is just the thing which `ControlTemplate in fact displays):

<ContentControl x:Name="ContentRoot">
   <ContentControl.ContentTemplate>
        <DataTemplate x:DataType="local:NutritionInfo">
                ... your template
        </DataTemplate>
   </ContentControl.ContentTemplate>
</ContentControl>

Note we use x:DataType to specify the type we bind to so that we can use x:Bind syntax. Finally, we update the template itself:

<TextBlock x:Name="lblCalorieGoal" Text="{x:Bind CalorieGoal}" ... />

We use x:Bind to bind the text of the TextBlock to the CalorieGoal property. We are almost done, now just set the Content property of the ContentControl to an instance of NutritionInfo (for example via data binding or directly):

ContentRoot.Content = new NutritionInfo()
{
    CalorieGoal = "1243"
};

Overall I recommend to read further about how data-binding works in XAML, as that will help you significantly simplify your code and avoid accessing controls directly via x:Name , and decouple UI from your code. See documentation for more info.