var serverWeightMap = new Dictionary<string, int>();
serverWeightMap.Add("192.168.1.100", 1);
serverWeightMap.Add("192.168.1.101", 1);

// 权重为 4
serverWeightMap.Add("192.168.1.102", 4);
serverWeightMap.Add("192.168.1.103", 1);
serverWeightMap.Add("192.168.1.104", 1);

// 权重为 3
serverWeightMap.Add("192.168.1.105", 3);
serverWeightMap.Add("192.168.1.106", 1);

// 权重为 2
serverWeightMap.Add("192.168.1.107", 2);
serverWeightMap.Add("192.168.1.108", 1);
serverWeightMap.Add("192.168.1.109", 1);
serverWeightMap.Add("192.168.1.110", 1);


int pos = 0;
// 加权轮询
public static string getRoundRobin()
{
    List<string> ipList = new List<string>();
    foreach(var key in serverWeightMap.Keys)
    {
        var weight = serverWeightMap[key];
        for(var i = 0; i < weight; i++)
            ipList.Add(key);
    }

    var ip = string.Empty;
    lock(pos)
    {
        if(pos > ipList.Count)
            pos = 0;

        ip = ipList[pos];
        pos++;
    }

    return ip;
}

// 加权随机
public static string getRandom()
{
    List<string> ipList = new List<string>();
    foreach(var key in serverWeightMap.Keys)
    {
        var weight = serverWeightMap[key];
        for(var i = 0; i < weight; i++)
            ipList.Add(key);
    }

    var randPos = Convert.ToInt32((new Random()).Next(ipList.Count));
    var ip = ipList[randPos];

    return ip;
}