JS对字符串字节长度处理：

String.prototype.gblen = function () {
    var len = 0;
    for (var i = 0; i < this.length; i++) {
        if (this.charCodeAt(i) > 127 || this.charCodeAt(i) == 94) {
            len += 2;
        } else {
            len++;
        }
    }
    return len;
}
String.prototype.gbtrim = function (len, s) {
    var str = '';
    var sp = s || '';
    var len2 = 0;
    for (var i = 0; i < this.length; i++) {
        if (this.charCodeAt(i) > 127 || this.charCodeAt(i) == 94) {
            len2 += 2;
        } else {
            len2++;
        }
    }
    if (len2 <= len) {
        return this;
    }
    len2 = 0;
    len = (len > sp.length) ? len - sp.length : len;
    for (var i = 0; i < this.length; i++) {
        if (this.charCodeAt(i) > 127 || this.charCodeAt(i) == 94) {
            len2 += 2;
        } else {
            len2++;
        }
        if (len2 > len) {
            str += sp;
            break;
        }
        str += this.charAt(i);
    }
    return str;
}

C#判断字节长度处理：

if (System.Text.Encoding.Default.GetByteCount(member.NICK) > 20 || System.Text.Encoding.Default.GetByteCount(member.NICK)<2) { sysResult = new SysResult("-1", "昵称的字符长度必须为2-20字节"); return Json(sysResult); }