I want to learn C# ASP MVC 5 with mongodb .

in Tutorial at http://www.c-sharpcorner.com/article/simple-crud-operation-using-asp-net-mvc-and-mongodb/ ,

My Connection in Attachment .

at command :
var carDetails = _dbContext._database.GetCollection<CarModel>("CarModel").FindAll().SetLimit(10).ToList();

I have a Error :

A timeout occured after 30000ms selecting a server using CompositeServerSelector{ Selectors = WritableServerSelector, LatencyLimitingServerSelector

{ AllowedLatencyRange = 00:00:00.0150000 }

}. Client view of cluster state is { ClusterId : "1", ConnectionMode : "Automatic", Type : "Unknown", State : "Disconnected", Servers : [{ ServerId: "

{ ClusterId : 1, EndPoint : "Unspecified/localhost:27017" }

", EndPoint: "Unspecified/localhost:27017", State: "Disconnected", Type: "Unknown", HeartbeatException: "MongoDB.Driver.MongoConnectionException: An exception occurred while opening a connection to the server. ---> MongoDB.Driver.MongoAuthenticationException: Unable to authenticate username 'demouser' on database 'CarDatabase'. ---> MongoDB.Driver.MongoCommandException: Command authenticate failed: auth failed.
at MongoDB.Driver.Core.WireProtocol.CommandWireProtocol`1.ProcessReply(ConnectionId connectionId, ReplyMessage`1 reply)
at MongoDB.Driver.Core.WireProtocol.CommandWireProtocol`1.<ExecuteAsync>d__11.MoveNext()
— End of stack trace from previous location where exception was thrown —
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MongoDB.Driver.Core.Authentication.MongoDBCRAuthenticator.<AuthenticateAsync>d__7.MoveNext()
— End of inner exception stack trace —
at MongoDB.Driver.Core.Authentication.MongoDBCRAuthenticator.<AuthenticateAsync>d__7.MoveNext()
— End of stack trace from previous location where exception was thrown —
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MongoDB.Driver.Core.Authentication.AuthenticationHelper.<AuthenticateAsync>d__1.MoveNext()
— End of stack trace from previous location where exception was thrown —
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MongoDB.Driver.Core.Connections.ConnectionInitializer.<InitializeConnectionAsync>d__3.MoveNext()
— End of stack trace from previous location where exception was thrown —
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MongoDB.Driver.Core.Connections.BinaryConnection.<OpenHelperAsync>d__48.MoveNext()
— End of inner exception stack trace —
at MongoDB.Driver.Core.Connections.BinaryConnection.<OpenHelperAsync>d__48.MoveNext()
— End of stack trace from previous location where exception was thrown —
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
at MongoDB.Driver.Core.Servers.ServerMonitor.<HeartbeatAsync>d__27.MoveNext()" }] }