.NET获得IP地址

/// <summary>
/// 获取访问者IP地址
/// </summary>
/// <returns></returns>
string GetHostAddress()
{
    string userIP = "127.0.0.1";

    try
    {
        if (System.Web.HttpContext.Current == null || System.Web.HttpContext.Current.Request == null || System.Web.HttpContext.Current.Request.ServerVariables == null)
            return "";

        string CustomerIP = "";

        //CDN加速后取到的IP 
        CustomerIP = System.Web.HttpContext.Current.Request.Headers["Cdn-Src-Ip"];
        if (!string.IsNullOrEmpty(CustomerIP))
        {
            return CustomerIP;
        }

        CustomerIP = System.Web.HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];


        if (!String.IsNullOrEmpty(CustomerIP))
            return CustomerIP;

        if (System.Web.HttpContext.Current.Request.ServerVariables["HTTP_VIA"] != null)
        {
            CustomerIP = System.Web.HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
            if (CustomerIP == null)
                CustomerIP = System.Web.HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
        }
        else
        {
            CustomerIP = System.Web.HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];

        }

        if (string.Compare(CustomerIP, "unknown", true) == 0)
            return System.Web.HttpContext.Current.Request.UserHostAddress;
        return CustomerIP;
    }
    catch { }

    return userIP;
}
/// <summary>
/// 检查IP地址格式
/// </summary>
/// <param name="ip"></param>
/// <returns></returns>
bool IsIP(string ip)
{
    return System.Text.RegularExpressions.Regex.IsMatch(ip, @"^((2[0-4]\d|25[0-5]|[01]?\d\d?)\.){3}(2[0-4]\d|25[0-5]|[01]?\d\d?)$");
}

public ActionResult Index(string systype)
{
    var ip = GetHostAddress();
}

public static class HttpRequestMessageExtensions
{
    private const string HttpContext = "MS_HttpContext";
    private const string RemoteEndpointMessage =
        "System.ServiceModel.Channels.RemoteEndpointMessageProperty";
    private const string OwinContext = "MS_OwinContext";

    public static string GetClientIpAddress(this HttpRequestMessage request)
    {
        // Web-hosting. Needs reference to System.Web.dll
        if (request.Properties.ContainsKey(HttpContext))
        {
            dynamic ctx = request.Properties[HttpContext];
            if (ctx != null)
            {
                return "" + ctx.Request.UserHostAddress;
            }
        }

        // Self-hosting. Needs reference to System.ServiceModel.dll. 
        if (request.Properties.ContainsKey(RemoteEndpointMessage))
        {
            dynamic remoteEndpoint = request.Properties[RemoteEndpointMessage];
            if (remoteEndpoint != null)
            {
                return "" + remoteEndpoint.Address;
            }
        }

        // Self-hosting using Owin. Needs reference to Microsoft.Owin.dll. 
        if (request.Properties.ContainsKey(OwinContext))
        {
            dynamic owinContext = request.Properties[OwinContext];
            if (owinContext != null)
            {
                return "" + owinContext.Request.RemoteIpAddress;
            }
        }

        return null;
    }
}

private void btn_GetIP_Click(object sender, EventArgs e)
{
    string url = "https://ip.cn/api/index?ip=&type=0";
    try
    {
        string result = GetUrl(url);

        string pattern = @"\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}";
        string ip = Regex.Match(result, pattern).ToString();
        txt_IP.Text = ip;
    }
    catch (Exception ex) { throw ex; }
}

private string GetUrl(string url)
{
    HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
    if (url.StartsWith("https", StringComparison.OrdinalIgnoreCase))
    {
        ServicePointManager.ServerCertificateValidationCallback = (object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors) => true;
        request.ProtocolVersion = HttpVersion.Version11;
        // 这里设置了协议类型。
        ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;// SecurityProtocolType.Tls1.2; 
        request.KeepAlive = false;
        ServicePointManager.CheckCertificateRevocationList = true;
        ServicePointManager.DefaultConnectionLimit = 100;
        ServicePointManager.Expect100Continue = false;
    }
    request.Method = "GET";    //使用get方式发送数据
    request.ContentType = "application/x-www-form-urlencoded";
    request.Referer = null;
    request.AllowAutoRedirect = true;
    request.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";
    request.Accept = "*/*";

    //获取网页响应结果
    HttpWebResponse response = (HttpWebResponse)request.GetResponse();
    Stream stream = response.GetResponseStream();
    //client.Headers.Add("Content-Type", "application/x-www-form-urlencoded");
    string result = string.Empty;
    using (StreamReader sr = new StreamReader(stream))
    {
        result = sr.ReadToEnd();
    }

    return result;
}

string IP = System.Net.Dns.GetHostEntry(System.Net.Dns.GetHostName()).AddressList.FirstOrDefault(address => address.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)?.ToString();

/// <summary>
/// 扩展类
/// </summary>
public static class Extension
{
    /// <summary>
    /// 获取客户Ip
    /// </summary>
    /// <param name="context"></param>
    /// <returns></returns>
    public static string GetClientUserIp(this HttpContext context)
    {
        var ip = context.Request.Headers["X-Forwarded-For"].FirstOrDefault();
        if (string.IsNullOrEmpty(ip))
        {
            ip = context.Connection.RemoteIpAddress.ToString();
        }
        return ip;
    }
}

string IP = HttpContext.GetClientUserIp();

/// <summary>
/// 
/// </summary>
/// <param name="app"></param>
/// <param name="env"></param>
/// <param name="loggerFactory"></param>
public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
    #region 解决Ubuntu Nginx 代理不能获取IP问题
    app.UseForwardedHeaders(new ForwardedHeadersOptions
    {
        ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto
    });
    #endregion       
}