WhichIsBetter.cs

// which is the better design, given StateArgs? A or B?
public class StateArgs
{
	public bool IsValid { get; set; }
	public string Value { get; set; }
}

// A
public static void ValidateState(StateArgs args)
{
	if(string.IsNullOrEmpty(args.Value))
		return;
	args.IsValid = Dictionary.Contains(args.Value);
}

// B
public static void ValidateState(StateArgs args)
{
	if(string.IsNullOrEmpty(args.Value))
		args.IsValid = false;
	else
		args.IsValid = Dictionary.Contains(args.Value);
}