截取字符串的两个方法

 public string GetContentSummary(string content, int length, bool StripHTML)
        {
            if (string.IsNullOrEmpty(content) || length == 0)
                return "";
            if (StripHTML)
            {
                System.Text.RegularExpressions.Regex re = new System.Text.RegularExpressions.Regex("<[^>]*>");
                content = re.Replace(content, "");
                content = content.Replace("　", "").Replace(" ", "").Replace("&nbsp;", "");
                if (content.Length <= length)
                    return content;
                else
                    return content.Substring(0, length) + "...";
            }
            else
            {
                if (content.Length <= length)
                    return content;

                int pos = 0, npos = 0, size = 0;
                bool firststop = false, notr = false, noli = false;
                System.Text.StringBuilder sb = new System.Text.StringBuilder();
                while (true)
                {
                    if (pos >= content.Length)
                        break;
                    string cur = content.Substring(pos, 1);
                    if (cur == "<")
                    {
                        string next = content.Substring(pos + 1, 3).ToLower();
                        if (next.IndexOf("p") == 0 && next.IndexOf("pre") != 0)
                        {
                            npos = content.IndexOf(">", pos) + 1;
                        }
                        else if (next.IndexOf("/p") == 0 && next.IndexOf("/pr") != 0)
                        {
                            npos = content.IndexOf(">", pos) + 1;
                            if (size < length)
                                sb.Append("<br />");
                        }
                        else if (next.IndexOf("br") == 0)
                        {
                            npos = content.IndexOf(">", pos) + 1;
                            if (size < length)
                                sb.Append("<br />");
                        }
                        else if (next.IndexOf("img") == 0)
                        {
                            npos = content.IndexOf(">", pos) + 1;
                            if (size < length)
                            {
                                sb.Append(content.Substring(pos, npos - pos));
                                size += npos - pos + 1;
                            }
                        }
                        else if (next.IndexOf("li") == 0 || next.IndexOf("/li") == 0)
                        {
                            npos = content.IndexOf(">", pos) + 1;
                            if (size < length)
                            {
                                sb.Append(content.Substring(pos, npos - pos));
                            }
                            else
                            {
                                if (!noli && next.IndexOf("/li") == 0)
                                {
                                    sb.Append(content.Substring(pos, npos - pos));
                                    noli = true;
                                }
                            }
                        }
                        else if (next.IndexOf("tr") == 0 || next.IndexOf("/tr") == 0)
                        {
                            npos = content.IndexOf(">", pos) + 1;
                            if (size < length)
                            {
                                sb.Append(content.Substring(pos, npos - pos));
                            }
                            else
                            {
                                if (!notr && next.IndexOf("/tr") == 0)
                                {
                                    sb.Append(content.Substring(pos, npos - pos));
                                    notr = true;
                                }
                            }
                        }
                        else if (next.IndexOf("td") == 0 || next.IndexOf("/td") == 0)
                        {
                            npos = content.IndexOf(">", pos) + 1;
                            if (size < length)
                            {
                                sb.Append(content.Substring(pos, npos - pos));
                            }
                            else
                            {
                                if (!notr)
                                {
                                    sb.Append(content.Substring(pos, npos - pos));
                                }
                            }
                        }
                        else
                        {
                            npos = content.IndexOf(">", pos) + 1;
                            sb.Append(content.Substring(pos, npos - pos));
                        }
                        if (npos <= pos)
                            npos = pos + 1;
                        pos = npos;
                    }
                    else
                    {
                        if (size < length)
                        {
                            sb.Append(cur);
                            size++;
                        }
                        else
                        {
                            if (!firststop)
                            {
                                sb.Append("...");
                                firststop = true;
                            }
                        }
                        pos++;
                    }

                }
                return sb.ToString();
            }
        }

 

 

 

 

        protected string CartStringn(int num1, string str)
        {
            int num = num1;
            foreach (char s in str.ToLower())
            {
                if (s == 'a' || s == 'b' || s == 'c' || s == 'd' || s == 'e' || s == 'f' || s == 'g' || s == 'h' || s == 'i' || s == 'j' || s == 'k' || s == 'l' || s == 'm' ||
                    s == 'n' || s == 'o' || s == 'p' || s == 'q' || s == 'r' || s == 's' || s == 't' || s == 'u' || s == 'v' || s == 'w' || s == 'x' || s == 'y' || s == 'z')
                    num++;
            }

            if (num > 0)
            {
                if (str.Length >= num)
                    return str.Substring(0, num) + "...";
                else
                    return str;
            }
            else
                return str;

        }