使用连接这些字符串的转换器：

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>

必须使用转换器绑定到集合。
问题是在集合改变时更新值（这里我的意思不是将值设置为新集合，而是向/从集合中添加/删除项）。
要实现在添加/删除时的更新，必须使用MultiBinding和ObservableCollection.Count的绑定之一，因此如果计数被更改，绑定属性将被更新。

<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.");
    }
}

创建一个额外的字符串属性，该属性将在每次集合项更改时更改：

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);}
    }
}

然后绑定到该属性：

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