public static String signTopRequest(Map<String, String> params, String secret, String signMethod) throws IOException {
    // 第一步：检查参数是否已经排序
    String[] keys = params.keySet().toArray(new String[0]);
    Arrays.sort(keys);

    // 第二步：把所有参数名和参数值串在一起
    StringBuilder query = new StringBuilder();
    if (Constants.SIGN_METHOD_MD5.equals(signMethod)) { //签名的摘要算法，可选值为：hmac，md5，hmac-sha256
        query.append(secret);
    }
    for (String key : keys) {
        String value = params.get(key);
        if (StringUtils.areNotEmpty(key, value)) {
            query.append(key).append(value);
        }
    }

    // 第三步：使用MD5/HMAC加密
    byte[] bytes;
    if (Constants.SIGN_METHOD_HMAC.equals(signMethod)) {
        bytes = encryptHMAC(query.toString(), secret);
    } else {
        query.append(secret);
        bytes = encryptMD5(query.toString());
    }

    // 第四步：把二进制转化为大写的十六进制(正确签名应该为32大写字符串，此方法需要时使用)
    //return byte2hex(bytes);
}

public static byte[] encryptHMAC(String data, String secret) throws IOException {
    byte[] bytes = null;
    try {
        SecretKey secretKey = new SecretKeySpec(secret.getBytes(Constants.CHARSET_UTF8), "HmacMD5");
        Mac mac = Mac.getInstance(secretKey.getAlgorithm());
        mac.init(secretKey);
        bytes = mac.doFinal(data.getBytes(Constants.CHARSET_UTF8));
    } catch (GeneralSecurityException gse) {
        throw new IOException(gse.toString());
    }
    return bytes;
}

public static byte[] encryptMD5(String data) throws IOException {
    return encryptMD5(data.getBytes(Constants.CHARSET_UTF8));
}
public static byte[] encryptMD5(byte[] data) throws IOException {
 byte[] bytes = null;
 try {
 MessageDigest md = MessageDigest.getInstance("MD5");
 bytes = md.digest(data);
 } catch (GeneralSecurityException gse) {
 throw new IOException(gse.toString());
 }
 return bytes;
}

public static String byte2hex(byte[] bytes) { StringBuilder sign = new StringBuilder(); for (int i = 0; i < bytes.length; i++) { String hex = Integer.toHexString(bytes[i] & 0xFF);if (hex.length() == 1) { sign.append("0"); }sign.append(hex.toUpperCase()); }return sign.toString(); } 

public static string SignTopRequest(IDictionary<string, string> parameters, string secret, string signMethod)
{
    // 第一步：把字典按Key的字母顺序排序
    IDictionary<string, string> sortedParams = new SortedDictionary<string, string>(parameters, StringComparer.Ordinal);
    IEnumerator<KeyValuePair<string, string>> dem = sortedParams.GetEnumerator();

    // 第二步：把所有参数名和参数值串在一起
    StringBuilder query = new StringBuilder();
    if (Constants.SIGN_METHOD_MD5.Equals(signMethod)) //签名的摘要算法，可选值为：hmac，md5，hmac-sha256
    {
        query.Append(secret);
    }
    while (dem.MoveNext())
    {
        string key = dem.Current.Key;
        string value = dem.Current.Value;
        if (!string.IsNullOrEmpty(key) && !string.IsNullOrEmpty(value))
        {
            query.Append(key).Append(value);
        }
    }

    // 第三步：使用MD5/HMAC加密
    byte[] bytes;
    if (Constants.SIGN_METHOD_HMAC.Equals(signMethod))
    {
        HMACMD5 hmac = new HMACMD5(Encoding.UTF8.GetBytes(secret));
        bytes = hmac.ComputeHash(Encoding.UTF8.GetBytes(query.ToString()));
    }
    else
    {
        query.Append(secret);
        MD5 md5 = MD5.Create();
        bytes = md5.ComputeHash(Encoding.UTF8.GetBytes(query.ToString()));
    }

    // 第四步：把二进制转化为大写的十六进制
    StringBuilder result = new StringBuilder();
    for (int i = 0; i < bytes.Length; i++)
    {
        result.Append(bytes[i].ToString("X2"));
    }

    return result.ToString();
}