using System.Collections.Generic;

class Program
{
    static void Main()
    {
        int[] xs = {1,2};
        List<byte> bs = new List<byte>();

        foreach (byte x in xs)
        { 
            bs.Add(x);
        }
    }
}

using System.Collections.Generic;

class Program
{
    static void Main()
    {
        int[] xs = {1,2};
        List<byte> bs = new List<byte>();

        for (int i = 0; i < xs.Length; i++)
        {
            byte x = xs[i]; // error CS0266: Cannot implicitly convert type 'int' to 'byte'. An explicit conversion exists (are you missing a cast?)
            bs.Add(x);
        }
    }
}

using System.Collections.Generic;

class Program
{
    static void Main()
    {
        int[] xs = {1,2};
        List<byte> bs = new List<byte>();

        for (int i = 0; i < xs.Length; i++)
        {
            byte x = (byte) xs[i]; // OK
            bs.Add(x);
        }
    }
}