C# (.NET HttpClient)

This guide shows how to set up a C# proxy with HttpClient, WebProxy, and NetworkCredential. You route .NET HTTP traffic through ColdProxy's gateway gw-{service-id}.coldproxy.com on any port in 30000-34999, working the same way on HttpClientHandler and the modern SocketsHttpHandler. It supports HTTP and HTTPS over TCP and (on .NET 6+) SOCKS5, and switches between rotating and sticky exits through ColdProxy's username tags. The examples use gw-2312.coldproxy.com (replace 2312 with your service/package ID) and the credentials from your client area. For background on the auth models, see IP whitelisting vs username/password.

#Connection details

#HttpClient proxy with WebProxy (HTTP/HTTPS)

Create a WebProxy for the gateway, attach a NetworkCredential, and pass it to a handler. ColdProxy auto-detects the protocol, so an http:// proxy scheme handles both HTTP and HTTPS targets.

using System;
using System.Net;
using System.Net.Http;
using System.Threading.Tasks;

var proxy = new WebProxy("http://gw-2312.coldproxy.com:30000")
{
    Credentials = new NetworkCredential("USERNAME", "PASSWORD")
};

var handler = new HttpClientHandler
{
    Proxy = proxy,
    UseProxy = true
};

using var client = new HttpClient(handler);
var body = await client.GetStringAsync("https://api.vipv6proxy.com/api/checker/my-ip");
Console.WriteLine(body); // JSON: {"ip": "...", "version": ..., "country": "...", ...}

For production, prefer SocketsHttpHandler (or IHttpClientFactory), which exposes pooling and connect-timeout controls. The proxy setup is identical:

using System.Net;
using System.Net.Http;

var handler = new SocketsHttpHandler
{
    Proxy = new WebProxy("http://gw-2312.coldproxy.com:30000")
    {
        Credentials = new NetworkCredential("USERNAME", "PASSWORD")
    },
    UseProxy = true,
    PooledConnectionLifetime = TimeSpan.FromMinutes(2)
};

using var client = new HttpClient(handler);

#SOCKS5 on .NET 6+

SocketsHttpHandler added native SOCKS4, SOCKS4a, and SOCKS5 support in .NET 6. Use a socks5:// scheme in the WebProxy URI. ColdProxy SOCKS5 runs over TCP and UDP.

using System.Net;
using System.Net.Http;

var proxy = new WebProxy("socks5://gw-2312.coldproxy.com:30000")
{
    Credentials = new NetworkCredential("USERNAME", "PASSWORD")
};

var handler = new SocketsHttpHandler { Proxy = proxy, UseProxy = true };
using var client = new HttpClient(handler);
var body = await client.GetStringAsync("https://api.vipv6proxy.com/api/checker/my-ip");
Console.WriteLine(body);

#Rotating vs sticky sessions

ColdProxy encodes geo-targeting and session behavior in the username, using a user-key-value-key-value... grammar (full reference: Username tag scheme). You switch between a fresh IP per request and a held IP by changing the username passed to NetworkCredential: no separate API call.

#Rotating (new IP per request)

With no session tag, each request gets a new IP. Add geo tags to target a country/state/city (here a rotating US exit):

// Rotating US exit IP — confirm the exact country prefix in your client area
var proxy = new WebProxy("http://gw-2312.coldproxy.com:30000")
{
    Credentials = new NetworkCredential("user-country-us", "PASSWORD")
};

#Sticky (hold the same IP)

A sticky session needs both a session tag and a time (duration) tag together; supplying only one rotates per request. This holds one US IP for 10 minutes:

// Sticky US IP for 10 minutes — same session ID + duration reuses the exit IP
var proxy = new WebProxy("http://gw-2312.coldproxy.com:30000")
{
    Credentials = new NetworkCredential("user-country-us-session-481516-time-10m", "PASSWORD")
};

For the concepts, see rotating and sticky proxies explained and geo-targeting with proxies.

#IP whitelist alternative

Authorize your server's public IP (up to 50 addresses) in the client area and you can skip credentials entirely; omit the NetworkCredential:

// IP-authenticated — no NetworkCredential
var handler = new HttpClientHandler
{
    Proxy = new WebProxy("http://gw-2312.coldproxy.com:30000"),
    UseProxy = true
};
using var client = new HttpClient(handler);

#Verify and troubleshoot

• Confirm reachability, exit IP, and location with the Proxy Checker and What Is My IP tools.
• A 407 almost always means credentials were set on the wrong object or embedded in the URL; keep them on WebProxy.Credentials. See Common errors & fixes and proxy error codes 407, 403, 429, 502, 504.
• On an IPv6 plan, check the target with the IPv6 Checker first; IPv4-only sites (no AAAA record) will fail over IPv6. See IPv6 reachability for the confirmed-platform list and CDN-aware routing.

#Next steps

• Compare plans and short paid validation options on pricing and the proxy product pages.
• See proxy automation and API integration for building rotation and provisioning into a .NET service.