Class DnsClient

A minimal DNS client for TXT record lookup (RFC 1035). Supports UDP transport with TCP fallback for truncated responses, configurable query timeout, and multiple nameservers.

Inheritance

object

DnsClient

Inherited Members

object.ToString()

object.Equals(object)

object.Equals(object, object)

object.ReferenceEquals(object, object)

object.GetHashCode()

object.GetType()

Namespace: DRIT.Mail.Rfc.Net

Assembly: DRIT.Mail.dll

Syntax

public sealed class DnsClient

Constructors

DnsClient()

Initializes a new instance of the DnsClient class with a default 5-second query timeout.

Declaration

public DnsClient()

DnsClient(TimeSpan)

Initializes a new instance of the DnsClient class with the specified query timeout.

Declaration

public DnsClient(TimeSpan queryTimeout)

Parameters

Type	Name	Description
TimeSpan	queryTimeout	The timeout for each DNS query attempt.

Methods

ResolveTxtRecords(string)

Resolves TXT records for the given domain name using the system's configured DNS nameservers.

Declaration

public IReadOnlyList<string> ResolveTxtRecords(string name)

Parameters

Type	Name	Description
string	name	The domain name to query (e.g., "selector._domainkey.example.com").

Returns

Type	Description
IReadOnlyList<string>	A list of TXT record values. Each entry is the concatenated character-string value of one TXT record in the answer section. Returns an empty list if no TXT records are found.

Exceptions

Type	Condition
ArgumentNullException	Thrown if name is null.
DnsException	Thrown if the query fails on all nameservers (timeout, network error, or server failure).

ResolveTxtRecords(string, params string[])

Resolves TXT records for the given domain name using the specified nameservers. Nameservers are tried in order; the first to return a definitive answer is used.

Declaration

public IReadOnlyList<string> ResolveTxtRecords(string name, params string[] nameservers)

Parameters

Type	Name	Description
string	name	The domain name to query.
string[]	nameservers	IPv4 or IPv6 addresses of DNS nameservers to query, in preference order.

Returns

Type	Description
IReadOnlyList<string>	A list of TXT record values. Returns an empty list if the name exists but has no TXT records, or if the name does not exist (NXDOMAIN).

Exceptions

Type	Condition
ArgumentNullException	Thrown if name or nameservers is null.
ArgumentException	Thrown if nameservers is empty.
DnsException	Thrown if all nameservers fail to respond.