Mobile Proxy for C# / .NET

In .NET you route an HttpClient through a proxy by handing it an HttpClientHandler whose Proxy is a WebProxy with NetworkCredential. This guide wires that to a mobile proxy and rotates the IP against the switch API.

7 min read·C# / .NET·Last updated: May 2026

Prerequisites

→
.NET 6+ SDK (dotnet --version). Everything here is in the BCL — no NuGet packages.
→
A mobile proxy slot, port, username, password and API key from mobileproxies.org.
→
Credentials read from environment variables, never hard-coded.

Step-by-Step Configuration

STEP 01

Read credentials from the environment

using System;

string host   = Environment.GetEnvironmentVariable("MP_HOST")!;      // proxy.mobileproxies.org
int    port   = int.Parse(Environment.GetEnvironmentVariable("MP_HTTP_PORT")!); // 8000
string user   = Environment.GetEnvironmentVariable("MP_USER")!;
string pass   = Environment.GetEnvironmentVariable("MP_PASS")!;
string slot   = Environment.GetEnvironmentVariable("MP_SLOT")!;
string apiKey = Environment.GetEnvironmentVariable("MP_API_KEY")!;

STEP 02

HttpClientHandler with WebProxy

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

var proxy = new WebProxy($"http://{host}:{port}")
{
    Credentials = new NetworkCredential(user, pass),
    // Send all traffic through the proxy, including localhost
    BypassProxyOnLocal = false,
};

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

var client = new HttpClient(handler)
{
    Timeout = TimeSpan.FromSeconds(30),
};

STEP 03

Send a request

using System;

HttpResponseMessage response =
    await client.GetAsync("https://example.com");

Console.WriteLine($"status: {(int)response.StatusCode}");

STEP 04

Reuse one client (don't recreate per request)

HttpClient is meant to be long-lived. Create one per proxy configuration and share it — recreating it per request exhausts sockets under load.

public static class Mp
{
    public static readonly HttpClient Client = BuildProxiedClient();

    private static HttpClient BuildProxiedClient()
    {
        var proxy = new WebProxy(
            $"http://{Environment.GetEnvironmentVariable("MP_HOST")}:" +
            $"{Environment.GetEnvironmentVariable("MP_HTTP_PORT")}")
        {
            Credentials = new NetworkCredential(
                Environment.GetEnvironmentVariable("MP_USER"),
                Environment.GetEnvironmentVariable("MP_PASS")),
        };
        return new HttpClient(new HttpClientHandler { Proxy = proxy });
    }
}

Verify It Works

Fetch api.ipify.org through the client and print the egress IP. It should be a carrier-owned mobile IP, never your machine's real address.

string ip = await client.GetStringAsync("https://api.ipify.org");
Console.WriteLine($"Egress IP: {ip}"); // e.g. 100.42.x.x on a mobile ASN

Rotate the IP

Request a fresh carrier IP with a POST to the switch endpoint. This call goes direct (a plain HttpClient, not the proxied one) and authenticates with your API key:

using System.Net.Http.Headers;

async Task RotateAsync(string slot, string apiKey)
{
    using var direct = new HttpClient();

    var request = new HttpRequestMessage(
        HttpMethod.Post,
        $"https://buy.mobileproxies.org/api/v1/proxies/{slot}/switch");
    request.Headers.Authorization =
        new AuthenticationHeaderValue("Bearer", apiKey);

    var resp = await direct.SendAsync(request);
    Console.WriteLine($"rotate -> {(int)resp.StatusCode}");

    await Task.Delay(TimeSpan.FromSeconds(4)); // let the new IP bind
}

Troubleshooting

407 Proxy Authentication Required

The WebProxy.Credentials were not set or were empty. Build a NetworkCredential(user, pass) and confirm both values came through from the environment.

SocketException / port exhaustion under load

You are creating a new HttpClient per request. Reuse one instance (Step 04) or register it via IHttpClientFactory so sockets are pooled correctly.

IP doesn't change after a rotate

.NET keeps connections alive. After switching, allow a few seconds for the pooled connection to recycle, or set a short PooledConnectionLifetime on a SocketsHttpHandler.

Related Guides

Reference

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