4、替换空格 C#实现

class Program
    {
        static void Main(string[] args)
        {
            string str = "We are Happy!";
            Console.WriteLine(ChangeSpaceToString(str, "%20"));
            Console.Read();
        }

        static string ChangeSpaceToString(string str, string strJoin)
        {
            #region  法一
            char[] ch = { ' ' };
            string[] strs = str.Split(ch, StringSplitOptions.RemoveEmptyEntries);

            string strNew = string.Join(strJoin, strs);

            return strNew;
            #endregion

            #region  法二
            //StringBuilder sb = new StringBuilder();

            //for (int i = 0; i < strs.Length - 1; i++)
            //{
            //    sb.Append(strs[i].ToString() + strJoin);
            //}
            //string strNew = sb.ToString() + strs[strs.Length - 1];
            //return strNew;
            #endregion
        }
    }