Summary

Error is thrown whenever I try to instantiate a MongoClient or a MongoClientSettings object (from MongoDB.Driver) when passing the connection string to their constructor, when running in Xamarin. 

{System.TypeInitializationException: The type initializer for ‘MongoDB.Driver.Core.Misc.DnsClientWrapper’ threw an exception. —> System.AggregateException: Error resolving name servers (Object reference not set to an instance of an object.) (Could not find file “/etc/resolv.conf”) —> System.NullReferenceException: Object reference not set to an instance of an object. at DnsClient.NameServer.QueryNetworkInterfaces () [0x0004c] in <519bb9af32234e5dba6bd0b076a88151>:0 at DnsClient.NameServer.ResolveNameServers (System.Boolean skipIPv6SiteLocal, System.Boolean fallbackToGooglePublicDns) [0x0005e] in <519bb9af32234e5dba6bd0b076a88151>:0 — End of inner exception stack trace — at DnsClient.NameServer.ResolveNameServers (System.Boolean skipIPv6SiteLocal, System.Boolean fallbackToGooglePublicDns) [0x00192] in <519bb9af32234e5dba6bd0b076a88151>:0 at DnsClient.LookupClient…ctor (DnsClient.LookupClientOptions options, DnsClient.DnsMessageHandler udpHandler, DnsClient.DnsMessageHandler tcpHandler) [0x000bc] in <519bb9af32234e5dba6bd0b076a88151>:0 at DnsClient.LookupClient…ctor (DnsClient.LookupClientOptions options) [0x00000] in <519bb9af32234e5dba6bd0b076a88151>:0 at DnsClient.LookupClient…ctor () [0x00006] in <519bb9af32234e5dba6bd0b076a88151>:0 at MongoDB.Driver.Core.Misc.DnsClientWrapper…ctor () [0x00006] in :0 at MongoDB.Driver.Core.Misc.DnsClientWrapper…cctor () [0x00000] in :0 — End of inner exception stack trace — at MongoDB.Driver.Core.Configuration.ConnectionString…ctor (System.String connectionString) [0x00000] in :0 at MongoDB.Driver.MongoUrlBuilder.Parse (System.String url) [0x00000] in <27273b0202ea4c34867b683ed7b21818>:0 at MongoDB.Driver.MongoUrlBuilder…ctor (System.String url) [0x00006] in <27273b0202ea4c34867b683ed7b21818>:0 at MongoDB.Driver.MongoUrl…ctor (System.String url) [0x00000] in <27273b0202ea4c34867b683ed7b21818>:0 at MongoDB.Driver.MongoClientSettings.FromConnectionString (System.String connectionString) [0x00000] in <27273b0202ea4c34867b683ed7b21818>:0 at --REDACTED FILENAME–

This issue is only happening when I run this code in a Xamarin project. I have the exact same code in a .NET 6 project and everything works fine there. The Xamarin project on the other hand targets .NET Standard 2.0 (also tried 2.1 with same issue) and I’ve been debugging it in an Android 12 device. The driver versions I’ve tested are 2.4.4 and 2.18.0. IDE is Visual Studio Version 17.2.0

Please provide the version of the driver. If applicable, please provide the MongoDB server version and topology (standalone, replica set, or sharded cluster).

How to Reproduce

The lines of code that cause this error are:

{{}}

{{string connString = "mongodb+srv://" + user + ":" + secret + "@" + server "/" project +"?retryWrites=true&w=majority"; }}
{{var settings = MongoClientSettings.FromConnectionString(connString); }}
{{settings.ServerApi = new ServerApi(ServerApiVersion.V1); }}
var mongoClient = new MongoClient(settings);

It will break at MongoClientSettings.FromConnectionString(connString);
Or this will also break:

{{}}

{{string connString = "mongodb+srv://" + user + ":" + secret + "@" + server + "/"+ project +"?retryWrites=true&w=majority"; }}
var mongoClient = new MongoClient(connString);

Additional Background

This issue is only happening when I run this code in a Xamarin project. I have the exact same code in a .NET 6 project and everything works fine there. The Xamarin project on the other hand targets .NET Standard 2.0 (also tried 2.1 with same issue) and I’ve been debugging it in an Android 12 device. The driver versions I’ve tested are 2.4.4 and 2.18.0. IDE is Visual Studio Version 17.2.0