DnsClient.NET is a high-performance open-source DNS lookup library for .NET developers who need to query DNS records programmatically from C# applications.

What it is

DnsClient.NET is a C# library, published on NuGet as the DnsClient package and licensed under Apache-2.0, that lets applications perform DNS lookups directly rather than shelling out to external tools. It provides both a synchronous and an asynchronous API centered on the LookupClient class, which can be instantiated with no arguments to pick up the local system's configuration, or configured with explicit nameservers, caching behaviour, and error handling. The project lives in the .NET and .NET Core ecosystem and is built from source with the latest .NET SDKs and Visual Studio 2022.

The concrete problem it solves is that .NET provides no convenient, complete way to issue DNS queries and read resource records without resorting to platform-specific calls or parsing the output of a command-line resolver. DnsClient.NET replaces that by speaking the DNS protocols directly, handling UDP lookups with automatic TCP fallback when a response is truncated (enabled by default), configurable EDNS support to adjust the default UDP buffer size and request security-relevant records, and both query-result caching based on record TTL and caching that can be disabled entirely.

Key capabilities

• Queries over UDP with configurable TCP fallback when the UDP result is truncated, plus EDNS support for adjusting the default UDP buffer size.
• A TTL-based query result cache with configurable minimum TTL, maximum TTL, and the option to disable caching altogether.
• Automatic nameserver discovery from local system configuration, including DNS servers set on network interfaces and Windows-specific NRPT policies, alongside explicit multi-endpoint configuration used in random or sequential order with retries.
• Support for a wide range of resource records: A, AAAA, NS, CNAME, SOA, MX, TXT, CAA, SRV, PTR for reverse lookups, and DNSSEC-related records including RRSIG, NSEC, NSEC3, DNSKEY, and DS.
• AXFR zone transfer, which requires LookupClient to be set to TCP mode only for that query type.
• An optional audit trail of each response and exception, optional trace and logging, and configurable error handling where DNS errors such as NotExistentDomain do not throw by default.
• SRV service-discovery queries with helper extensions on LookupClient.

Who uses it and how

• .NET application developers embed LookupClient in service code to resolve hostnames, as in the README's example of awaiting QueryAsync("google.com", QueryType.A) and reading result.Answers.ARecords().
• Operators running applications against multiple configured DNS endpoints rely on the random or sequential endpoint ordering and configurable retries for resilience.
• Projects that need controlled cache behaviour in high-traffic, low-latency settings set a minimum TTL — even a few milliseconds — so responses are always cached for at least that long.
• Teams working with Windows environments can depend on nameserver auto discovery that honours NRPT policy configuration rather than hardcoding resolvers.
• Contributors and evaluators build the project from source and follow the MiniDig sample command-line tool and the separate DnsClient.NET.Samples repository for further usage patterns.

Getting started

Install the library from NuGet with the package name DnsClient, then instantiate new LookupClient() and call QueryAsync with a query name and query type; additional documentation and examples are on the project site at https://dnsclient.michaco.net.

How it compares

DnsClient.NET stands alone in this registry among comparable tools named in its documentation.

When to use it — and when not

Choose it when you are writing .NET code and need direct, cacheable, protocol-level DNS queries with a broad record-type surface; it is a library you embed, not a service, so there is no database, storage, or SMTP to operate, only the DNS servers you point it at. Avoid it if you need a DNS server rather than a client, or if you require a command-line dig-style tool as a dependency, and note that the README itself is brief, deferring to an external site for full documentation, with 21 open issues currently outstanding.

var lookup = new LookupClient();
var result = await lookup.QueryAsync("google.com", QueryType.A);

var record = result.Answers.ARecords().FirstOrDefault();
var ip = record?.Address;