C# mongo-csharp-driver 2.4.4权限 身份登录

C# mongo-csharp-driver权限 身份登录。shell端没问题。C#的登录总报授权错误，MongoCommandException

 var connectionString =
                "mongodb://user1:password1@somehost/?appname=app;" +
                "connect=direct;connectTimeout=123;uuidRepresentation=pythonLegacy;ipv6=true;heartbeatInterval=1m;heartbeatTimeout=2m;" +
                "maxIdleTime=124;maxLifeTime=125;maxPoolSize=126;minPoolSize=127;readConcernLevel=majority;" +
                "readPreference=secondary;readPreferenceTags=a:1,b:2;readPreferenceTags=c:3,d:4;localThreshold=128;socketTimeout=129;" +
                "serverSelectionTimeout=20s;ssl=true;sslVerifyCertificate=false;waitqueuesize=130;waitQueueTimeout=131;" +
                "w=1;fsync=true;journal=true;w=2;wtimeout=131;gssapiServiceName=other";
            var builder = new MongoUrlBuilder(connectionString);
            var url = builder.ToMongoUrl();
            var settings = MongoClientSettings.FromUrl(url);


            // a few settings can only be made in code,关键是这个，没有开发环境，不保证语法正确
            settings.Credentials = new[] { MongoCredential.CreateCredential("mydb", builder.username, builder.password) };
            

 var client1 = new MongoClient(settings );