abc and cba become ILoveYou become IevoLuoY

abc->cba

    Console.WriteLine("请输入：");
    string str = Console.ReadLine();
    char[] chs = str.ToCharArray();
    char[] chs1 = new char[chs.Length];
    for (int i = chs.Length - 1, j = 0; i >= 0; i--, j++)
    {

        chs1[j] = chs[i];

    }
    string str1 = new string(chs1);
    Console.WriteLine(str1);

I Love You->I evoL uoY

    Console.WriteLine("请输入：");
    string str = Console.ReadLine();
    string[] strNew = str.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
    for (int i = 0; i < strNew.Length; i++)
    {
        char[] chs = strNew[i].ToCharArray();
        for (int j = 0; j < chs.Length / 2; j++)
        {
        char temp = chs[j];
        chs[j] = chs[chs.Length - 1 - j];
        chs[chs.Length - 1 - j] = temp;
        }
        strNew[i] = new string(chs);
    }
    str = string.Join(" ", strNew);
    Console.WriteLine(str);