How to Fix DNS Resolution Error in C#

A DNS Resolution Error in C# usually signals a straightforward configuration problem. Here's exactly how to fix it.

Understanding the Problem

DNS resolution errors in C# occur when the runtime can't resolve a hostname to an IP address. This may be caused by misconfigured DNS servers, IPv6/IPv4 issues, network connectivity problems, or transient DNS cache failures.

Solution

The key is to use SocketsHttpHandler with explicit timeouts and verify DNS resolution:

var handler = new SocketsHttpHandler
{
    ConnectTimeout = TimeSpan.FromSeconds(10),
    PooledConnectionIdleTimeout = TimeSpan.FromMinutes(2),
    EnableMultipleHttp2Connections = true,
};

var client = new HttpClient(handler);
var addresses = await Dns.GetHostAddressesAsync("api.example.com");
Console.WriteLine($"Resolved: {addresses[0]}");

Common Pitfall

Don't overlook your CI/CD pipeline — sometimes the fix works locally but the deployment environment has different defaults. Make sure your C# configuration is explicit rather than relying on defaults. Review your C# project's dependency tree after applying this fix. Outdated packages are a common source of subtle incompatibilities.

Confirming It Works

To confirm the fix is working, check your C# application logs for any remaining error traces. You should see clean request/response cycles without the previous error. Deploy to a staging environment to verify the fix holds under production-like conditions.

Going Forward

Want to catch errors like this before they reach production? [Bugsly](https://bugsly.dev) provides real-time error tracking for C# applications.