public class Class1
{
    public int Test1;
}
public class Class2
{
    public int Test2;
    public static implicit operator Class1(Class2 item)
    {
        return new Class1 { Test1 = item.Test2 };
    }
}

List<Class2> items = new List<Class2> { new Class2 { Test2 = 9 } };

foreach (Class1 item in items)
{
    Console.WriteLine(item.Test1);
}

foreach (Class1 item in items.ConvertAll<Class1>(i=>i))
{
    Console.WriteLine(item.Test1);
}

foreach (Class1 item in items.Select<Class2, Class1>(i=> i))
{
    Console.WriteLine(item.Test1);
}

foreach (Class1 item in items.Select(i=>i))
{
    Console.WriteLine(item.Test1);
}

List<byte> items = new List<byte> { 1, 2, 3, 4 };

foreach (int i in items) // since bytes implictly cast to ints
{
    Console.WriteLine(i + 1000);
}