c# 对接第三方接口实现签名

using System.Drawing;
using System.Text;
using System;
using static System.Net.Mime.MediaTypeNames;
using System.Reflection;
using System.Xml;
using System.Collections.Generic;
using System.Xml.Linq;
using System.Linq;


Console.Write("开始：");
UTF8LengthPadding.Main();
Console.ReadLine();


public class UTF8LengthPadding
{
    public static void Main()
    {
        //秘钥
        string appsecret = "12345";
        //参数类
        Parm parm = new Parm();
        //存放参数数据的集合
        Dictionary<string, string> dic = new Dictionary<string, string>();
        //循环类 添加到集合中
        Type myEntityType = parm.GetType();
        PropertyInfo[] properties = myEntityType.GetProperties();
        foreach (PropertyInfo property in properties)
        {
            string propertyName = property.Name;
            object propertyValue = property.GetValue(parm);
            dic.Add(propertyName, propertyValue.ToString());
        }
        //对key进行排序
        var sortedKeys = dic.OrderBy(kvp => kvp.Key).ToDictionary(kvp => kvp.Key);
        //拼接结果
        string prestr = "";
        //最终结果
        string finalStr = "";
        foreach (var item in sortedKeys.Keys)
        {
            //key的长度
            int keyLength = item.Length;
            //不足两位补0
            string key = keyLength.ToString("00");
            //拼接
            prestr = prestr + key;
            //组装key值
            prestr = prestr + "-" + item + ":";

            //组装value长度
            string valueStr = dic[item];
            //value长度
            int valueLength = valueStr.Length;
            //不足四位补0
            string value = valueLength.ToString("0000");
            //拼接
            prestr = prestr + value;
            //组装value
            prestr = prestr + "-" + valueStr + ";";
        }
        //去掉最后一个;
        if (prestr.Length > 0)
        {
            prestr = prestr.Substring(0, prestr.Length - 1);
        }

        //第三步 计算sign md5加密后,返回的是32位小写的MD5值
        finalStr = prestr + appsecret;
        Console.WriteLine(finalStr); // 输出
        Console.WriteLine(GetMD5_32(finalStr)); // 输出
    }

    /// <summary>
    /// 获得32位的MD5加密
    /// </summary>
    /// <param name="input"></param>
    /// <returns></returns>
    public static string GetMD5_32(string input)
    {
        System.Security.Cryptography.MD5 md5 = System.Security.Cryptography.MD5.Create();
        byte[] data = md5.ComputeHash(System.Text.Encoding.Default.GetBytes(input));
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < data.Length; i++)
        {
            sb.Append(data[i].ToString("x2"));
        }
        return sb.ToString();
    }
}

public class Parm 
{
    public string appkey { get; set; } = "test2-xx";
    public string page_no { get; set; } = "0";
    public string end_time { get; set; } = "2016-08-01 13:00:00";
    public string start_time { get; set; } = "2016-08-01 12:00:00";
    public string page_size { get; set; } = "40";
    public string sid { get; set; } = "test2";
    public string timestamp { get; set; } = "1470042310";
}