C#根据字节数截取字符串

        /// <summary>
        /// 按最大字节数,截取字符串
        /// </summary>
        /// <param name="value">要截取的字符串</param>
        /// <param name="length">最大长度</param>
        /// <returns></returns>
        private string Intercept(string value, int length)
        {
            if (value.Length * 2 <= length)
            {
                return value;
            }
            string newvalue;
            for (int i = length / 2; i < value.Length; i++)
            {
                newvalue = value.Substring(0, i);
                if (Encoding.Default.GetByteCount(newvalue) > length)
                {
                    return value.Substring(0, i - 1);
                }
            }
            return value;
        }

正确替换多个匹配内容

private void button1_Click(object sender, EventArgs e)
{
    Regex regx = new Regex(@"\[image\]", RegexOptions.IgnoreCase);
    string content = textBox1.Text;
   
    Match m = regx.Match(content);
    while (m.Success)
    {
        content = content.Remove(m.Index, m.Value.Length);
        content = content.Insert(m.Index, "[picture]");
        m = regx.Match(content);

    }

    textBox2.Text = content;
}

 方法二:

private void button1_Click(object sender, EventArgs e)
{
    Regex regx = new Regex(@"\[image\]", RegexOptions.IgnoreCase);
    string content = textBox1.Text;
    content=regx.Replace(content, new MatchEvaluator(DoMatch)); 
    textBox2.Text = content;
}

private string DoMatch(Match m)
{
    return "[picture]";
}

function fmt(s) {

            var value = s.replace(/,/g, "");

            var v = value.replace(/(\d+)(\.\d+)?/, "$1");

            var d = value.replace(/(\d+)(\.\d+)?/, "$2");

            var reg = /\d{4,}\b/;

            while (reg.test(v)) {

                v = v.replace(/(\d{3})\b/, ',$1');

            }

            return v + d; ;

        }