softlion / Heijden.Dns

A reusable DNS resolver for .NET, PCL version.

Heijden.Dns.Portable

A reusable DNS resolver for .NET, using netstandard 1.3

Quick start

Add this library to your pcl project.

Important note: if the project referencing this library and/or the startup project of your solution is not using 'project.json' (ie: it uses packages.config), then you need to add the following nuget packages too, otherwise strange errors/crashes will occur:

System.Net.NetworkInformation v4.3.0+
System.Net.Sockets v4.3.0+

Sample Usage

Get SRV records:

var domainName = "_autoconfig._tcp.local.";
var resolver = new Resolver();
var response = await resolver.Query(domainName, QType.SRV);
if (String.IsNullOrEmpty(response.Error))
{
    var servers = response.RecordsSRV;
    foreach (var item in servers.OrderBy(it => it.PRIORITY).ThenBy(it => it.WEIGHT))
        Console.WriteLine($"SRV: {item.TARGET}:{item.PORT} priority:{item.PRIORITY} weight:{item.WEIGHT} ");
}

Note on Android

There is a bug in the on Android: it does not detect the dns addresses.
Use this code instead then set the dns server address:

    {...
            var resolver = new Resolver
            {
                DnsServers = GetDnsServersOnAndroid().ToArray()
            };
    ...}

    public static IEnumerable<IPEndPoint> GetDnsServersOnAndroid()
    {
        var dnsEntries = new List<string>();
        try
        {
            var systemPropertiesClass = Java.Lang.Class.ForName("android.os.SystemProperties");
            var getMethod = systemPropertiesClass.GetMethod("get", Java.Lang.Class.FromType(typeof(Java.Lang.String)));
            //var serialnumber = (Java.Lang.String)getMethod.Invoke(systemPropertiesClass, "ril.serialnumber");
            for (var i = 1; i < 8; i++)
            {
                var value = ((Java.Lang.String)getMethod.Invoke(null, $"net.dns{i}"))?.ToString();
                if (!String.IsNullOrEmpty(value) && !dnsEntries.Contains(value))
                    dnsEntries.Add(value);
            }
        }
        catch (Java.Lang.Exception e)
        {
            System.Diagnostics.Debug.WriteLine(e.Message);
        }

        return dnsEntries.Select(entry => new IPEndPoint(IPAddress.Parse(entry), 53)).ToList();
    }