c# 替换所有中文、标点符号，全角转半角

 　　　　private void btnStart_Click(object sender, EventArgs e)
        {
            var srcWords = ToDBC(txtSrc.Text.Trim());
            var placeStr = Regex.Replace(srcWords, @"([p{P}*])", " ");
            placeStr = Regex.Replace(placeStr,@"([u4e00-u9fa5])", "");
            var splitWords = placeStr.Split(new string[] { " " }, StringSplitOptions.RemoveEmptyEntries);
            var words = splitWords.ToList().Select(item =>
            {
                if (item.Length > 0)
                {
                    var first = item.Substring(0, 1).ToUpper();
                    var last = "";
                    if (item.Length > 2)
                    {
                        last = item.Substring(1, item.Length-1);
                    }
                    return first + last;
                }
                return "";
            });
            var joinWords = string.Join(" ", words);
            Clipboard.SetText(joinWords);

            txtDes.Text = AppendWords(joinWords);
            MessageBox.Show("已将替换后的字符串复制到粘贴板");
        }

        /// <summary>
        /// 替换所有的中文及标点符号
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        string RemoveAllChineseAndSymbol(string str)
        {
            var placeStr = Regex.Replace(str, @"([p{P}*])", " ");
            placeStr = Regex.Replace(placeStr, @"([u4e00-u9fa5])", "");
            return placeStr;
        }
        /// <summary>
        /// 追加及替换内容
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        string AppendWords(string str)
        {
            var append = Regex.Replace(ToDBC(txtAppend.Text.Trim()), @"[p{P}*]", " ");
            if (string.IsNullOrEmpty(append))
            {
                return str;
            }
            var i=combSelect.SelectedIndex;
            
            if (i==0)
            {
                return str.Trim() + " " + append;
            }else if (i==1)
            {
                return append + " " + str.Trim();
            }else if (i==2)
            {
                var replaceTo=Regex.Replace(ToDBC(txtToReplace.Text.Trim()), @"[p{P}*]", " ");
                return str.Trim().Replace(append, replaceTo);
            }
            else
            {
                return str;
            }
        }
        /// <summary>
        /// 全角转半角
        /// </summary>
        /// <param name="input"></param>
        /// <returns></returns>
        public string ToDBC(string input)
        {
            char[] c = input.ToCharArray();
            for (int i = 0; i < c.Length; i++)
            {
                if (c[i] == 12288)
                {
                    c[i] = (char)32;
                    continue;
                }
                if (c[i] > 65280 && c[i] < 65375)
                    c[i] = (char)(c[i] - 65248);
            }
            return new String(c);
        }

        private void combSelect_SelectedIndexChanged(object sender, EventArgs e)
        {
            var cb=(ComboBox) sender;
            txtToReplace.Visible = cb.SelectedIndex==2;
        }