Help me to understand why Select causes a retention

Hello,

I was profiling a WPF application while I encountered a small memory retention...

I have this base class which's a viewmodel 

public class ManageFontModelBase<T> where T:class
 {
 public ObservableCollection<string> Fonts { get; set; }

public ObservableCollection<string> FontStyles { get; set; }

public ObservableCollection<string> FontSizes { get; set; }

public T Grid { get; set; }

public ManageFontModelBase()
 {
 Fonts = new ObservableCollection<string>();
 FontStyles = new ObservableCollection<string>();
 FontSizes=new ObservableCollection<string>();

var installedFontCollection = new InstalledFontCollection();

Fonts = new ObservableCollection<string>(installedFontCollection.Families.Select(x => x.Name));
 FontStyles = new ObservableCollection<string>(typeof(FontStyles).GetProperties().Select(x => x.Name));

for (int i = 6; i < 79; i = i + 2)
 {
 FontSizes.Add($"{i}");
 }
 }
 }

DotMemoring it (TM!) I got those two retention

The only way I've found to remove them is to do so

public ManageFontModelBase()
 {
 Fonts = new FastObservableCollection<string>();
 FontStyles = new FastObservableCollection<string>();
 FontSizes=new FastObservableCollection<string>();

using (var installedFontCollection = new InstalledFontCollection())
 {
 var fonts = installedFontCollection.Families
 .ToList();

foreach (var font in fonts)
 {
 Fonts.Add(font.Name);
 }
 }

var propertyInfos = typeof(FontStyle).GetProperties();//.Select(p=>p.Name).ToList();

using (FontStyles.SuspendChangeNotifications())
 {
 foreach (var propertyInfo in propertyInfos)
 {
 FontStyles.Add(propertyInfo.Name);
 }
 }

using (FontSizes.SuspendChangeNotifications())
 {
 for (var i = MinFontSize; i < MaxFontSize; i = i + FontSizeStep)
 {
 FontSizes.Add($"{i}");
 }
 }
 }


Why the Select cause those leak? Is it correct the way I've fixed it?

Thanks