using System;

using System.Collections.ObjectModel;

using System.Linq;

public class Program

{

    private static ObservableCollection<Record> myCollection;

    public static void Main()

    {

        //myCollection is null

        SetLoadingProperty(true);

        // myCollection doesn't hold any items

        myCollection = new ObservableCollection<Record>();

        SetLoadingProperty(true);

        // myCollection holds one item

        myCollection.Add(new Record());

        SetLoadingProperty(true);

        Console.WriteLine(string.Join("", myCollection.Select(x => "IsLoading="+x.IsLoading)));

    }

    public static void SetLoadingProperty(bool isLoading)

    {

        if (myCollection == null)

            return;

​

        foreach(var record in myCollection)

        {

            record.IsLoading = isLoading;

        }

    }

}

​

public class Record

{

    public bool IsLoading {get;set;}

}