An example of custom For syntax... Pretty dumb... Just messing around...

ForSyntax.cs

using System;

namespace Example
{
	class Program
	{
		static void Main()
		{
			For (10..5)
			(
				Console.WriteLine
			);

			For (5..10, Console.WriteLine);
		}

		public static Action<Action<int>> For(Range range) =>
			x =>
			{
				int a = range.Start.Value;
				int b = range.End.Value;
				if (a > b) for (int i = a; i >= b; i--) x(i);
				else for (int i = a; i <= b; i++) x(i);
			};

		public static void For(Range range, Action<int> action)
		{
			int a = range.Start.Value;
			int b = range.End.Value;
			if (a > b) for (int i = a; i >= b; i--) action(i);
			else for (int i = a; i <= b; i++) action(i);
		}
	}
}

ForSyntax2.cs

using System;
using static FOR;
public class Program
{
    public static int Main() =>
        For (1..4) > Console.WriteLine;
}
public struct FOR
{
    public static FOR For(Range range) => new FOR(range);
    public Range Value;
    public FOR(Range range) => Value = range;
    public static int operator >(FOR @for, Action<int> action)
    {
        for (int i = @for.Value.Start.Value; i < @for.Value.End.Value; i++)
            action(i);
        return default;
    }
    public static int operator <(FOR @for, Action<int> action) =>
        throw new NotImplementedException();
}