Binding all elements of ObservableCollection to TextBlock

Question

I am trying to bind a TextBlock to items in a ObservableCollection. TextBlock values should be generated up to elements from collection. Count of elements in collection is between 0 and 7 (if it helps). MyClass implemented INotifyPropertyChanged. It should be directly TextBlock, not ListBox. How can I do it? Thanks!
Update: The problem is that I don't know previously the number of elements in collection. I know that it is better to use ListBox or ListView in this case, but it's important to make it in TextBlock or Label

For example:

1. ObservableCollection contains elements 0, 1, 2.
   TextBlock should contains following "Values: 0, 1, 2"
   

2. ObservableCollection contains elements 0, 1.
   TextBlock should contains following "Values: 0, 1"
   

   <TextBlock>
          <Run Text="Values: "/>
          <Run Text="{Binding Values}" />                 
   </TextBlock>
   

ObservableCollection<int> values = new ObservableCollection<int>();
        public ObservableCollection<int> Values
        {
            get => values;
            set
            {
                values = value;
                OnPropertyChanged();
            }
        }

Answer 1

Use a Converter that concat those strings:

public class StringsCollectionConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value == null) return null;
        return string.Join("\n", value as ObservableCollection<string>);
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

Xaml

<Window.Resources>
    <local:StringsCollectionConverter x:Key="StringsCollectionConverter"/>
</Window.Resources> 
<Grid>
    <TextBlock Text="{Binding TextBlockCollection, Converter={StaticResource StringsCollectionConverter}}"></TextBlock>
</Grid>

Answer 2

You have to bind to the collection using a converter.
The problem is to get value updated on collection changed(here I mean not setting Values to new collection, but adding/removing items to/from the collection).
To implement updating on add/remove you have to use MultiBinding with one of bindings to the ObservableCollection.Count, so if the count be changed, then the bound property will be updated.

<Window.Resources>
    <local:MultValConverter x:Key="multivalcnv"/>
</Window.Resources> 
<TextBlock>
    <TextBlock.Text>
        <MultiBinding Converter="{StaticResource multivalcnv}">
            <Binding Path="Values"/>
            <Binding Path="Values.Count"/>
        </MultiBinding>
    </TextBlock.Text>
</TextBlock>

public class MultValConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        if (values.Length > 1 && values[0] is ICollection myCol)
        {
            var retVal = string.Empty;
            var firstelem = true;
            foreach (var item in myCol)
            {
                retVal += $"{(firstelem?string.Empty:", ")}{item}";
                firstelem = false;
            }

            return retVal;
        }
        else
            return Binding.DoNothing;
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException("It's a one way converter.");
    }
}

Answer 3

create an additional string property, which will change every time when collection item[s] change:

public class Vm
{
    public Vm()
    { 
       // new collection assigned via property because property setter adds event handler
       Values = new ObservableCollection<int>();
    }

    ObservableCollection<int> values;
    public ObservableCollection<int> Values
    {
        get => values;
        set
        {
            if (values != null) values.CollectionChanged -= CollectionChangedHandler;
            values = value;
            if (values != null) values.CollectionChanged += CollectionChangedHandler;
            OnPropertyChanged();
        }
    }

    private void CollectionChangedHandler(object sender, NotifyCollectionChangedEventArgs e)
    {
        OnPropertyChanged("ValuesText");
    }

    public string ValuesText
    {
        get { return "Values: " + String.Join(", ", values);}
    }
}

and then bind to that property:

<TextBlock Text="{Binding ValuesText}"/>