How do I log my queries in MongoDB C# Driver 2.0?

For newer C# MongoDB drivers the API has changed. You have to use the more complex constructor that accepts a MongoClientSettings object, instead of the connection string.

Use the following code to keep using a connection string, but enable the logging of each command:

var mongoConnectionUrl = new MongoUrl(connectionString);var mongoClientSettings = MongoClientSettings.FromUrl(mongoConnectionUrl);mongoClientSettings.ClusterConfigurator = cb => {    cb.Subscribe<CommandStartedEvent>(e => {        logger.Log($"{e.CommandName} - {e.Command.ToJson()}");    });};var mongoCfgClient = new MongoClient(mongoClientSettings);

You can enable logging by the mongo driver itself:

var settings = new MongoClientSettings{    ClusterConfigurator = cb =>    {        var textWriter = TextWriter.Synchronized(new StreamWriter("mylogfile.txt"));        cb.AddListener(new LogListener(textWriter));    }};

You can hook it up to log4net if you wish.

Logging to VS output with 2.7.3 driver.

using MongoDB.Bson;using MongoDB.Driver;using System;#if TRACEusing System.Diagnostics;using MongoDB.Driver.Core.Configuration;#endif...public static ClusterBuilder ConfigureCluster(ClusterBuilder builder){#if TRACE    var traceSource = new TraceSource(nameof(Geotagging), SourceLevels.Verbose);    builder.TraceWith(traceSource);    builder.TraceCommandsWith(traceSource);#endif    return builder;}public MongoClient BuildMongoClient(string connection_string){    var mongoUrlBuilder = new MongoUrlBuilder(connection_string);    var settings = MongoClientSettings.FromUrl(mongoUrlBuilder.ToMongoUrl());    settings.ClusterConfigurator = cb => ConfigureCluster(cb);    return new MongoClient(settings);}