CertificateUnknown error when connecting to Heroku Postgres database - asp.net

Question

So I am in the middle of migrating from SQL Server to PostgreSQL, and I am building a temporary solution for the migration period to allow my ASP.NET app to connect to my Heroku Postgres database and make use of Entity Framework etc.
So far I have managed to connect to the database from pgAdmin III for windows with no problems, but when connecting from ASP.NET app, I get this error:
CertificateUnknown: Server certificate was not accepted. Chain status: A certificate chain processed, but terminated in a root certificate which is not trusted by the trust provider.
. The specified hostname was not present in the certificate.
I am still fairly new to heroku, but it does not make sense why I can connect from pgAdmin with the same settings as my ASP.NET app but it doesn't work in the app itself.
Full stack trace:
[ClientAlertException: CertificateUnknown: Server certificate was not accepted. Chain status: A certificate chain processed, but
terminated in a root certificate which is not trusted by the trust
provider. . The specified hostname was not present in the
certificate.]
TlsClientStream.TlsClientStream.SendAlertFatal(AlertDescription
description, String message) +44
TlsClientStream.TlsClientStream.ParseCertificateMessage(Byte[] buf,
Int32& pos) +1359
TlsClientStream.TlsClientStream.TraverseHandshakeMessages() +415
TlsClientStream.TlsClientStream.GetInitialHandshakeMessages(Boolean
allowApplicationData) +336
TlsClientStream.TlsClientStream.PerformInitialHandshake(String
hostName, X509CertificateCollection clientCertificates,
RemoteCertificateValidationCallback
remoteCertificateValidationCallback, Boolean
checkCertificateRevocation) +198
[IOException: TlsClientStream.ClientAlertException:
CertificateUnknown: Server certificate was not accepted. Chain status:
A certificate chain processed, but terminated in a root certificate
which is not trusted by the trust provider. . The specified hostname
was not present in the certificate. at
TlsClientStream.TlsClientStream.SendAlertFatal(AlertDescription
description, String message) at
TlsClientStream.TlsClientStream.ParseCertificateMessage(Byte[] buf,
Int32& pos) at
TlsClientStream.TlsClientStream.TraverseHandshakeMessages() at
TlsClientStream.TlsClientStream.GetInitialHandshakeMessages(Boolean
allowApplicationData) at
TlsClientStream.TlsClientStream.PerformInitialHandshake(String
hostName, X509CertificateCollection clientCertificates,
RemoteCertificateValidationCallback
remoteCertificateValidationCallback, Boolean
checkCertificateRevocation)]
TlsClientStream.TlsClientStream.PerformInitialHandshake(String
hostName, X509CertificateCollection clientCertificates,
RemoteCertificateValidationCallback
remoteCertificateValidationCallback, Boolean
checkCertificateRevocation) +289
Npgsql.NpgsqlConnector.RawOpen(NpgsqlTimeout timeout) +1372
Npgsql.NpgsqlConnector.Open(NpgsqlTimeout timeout) +314
Npgsql.NpgsqlConnection.OpenInternal() +461
Npgsql.NpgsqlConnection.Open() +4
Npgsql.NpgsqlServices.UsingPostgresDBConnection(NpgsqlConnection
connection, Action`1 action) +162
Npgsql.NpgsqlServices.GetDbProviderManifestToken(DbConnection
connection) +99
System.Data.Entity.Core.Common.DbProviderServices.GetProviderManifestToken(DbConnection
connection) +87
[ProviderIncompatibleException: The provider did not return a
ProviderManifestToken string.]
System.Data.Entity.Core.Common.DbProviderServices.GetProviderManifestToken(DbConnection
connection) +271
System.Data.Entity.Utilities.DbProviderServicesExtensions.GetProviderManifestTokenChecked(DbProviderServices
providerServices, DbConnection connection) +27
[ProviderIncompatibleException: An error occurred accessing the
database. This usually means that the connection to the database
failed. Check that the connection string is correct and that the
appropriate DbContext constructor is being used to specify it or find
it in the application's config file. See
http://go.microsoft.com/fwlink/?LinkId=386386 for information on
DbContext and connections. See the inner exception for details of the
failure.]
System.Data.Entity.Utilities.DbProviderServicesExtensions.GetProviderManifestTokenChecked(DbProviderServices
providerServices, DbConnection connection) +89
System.Data.Entity.Infrastructure.<>c__DisplayClass1.b__0(Tuple3
k) +31
System.Collections.Concurrent.ConcurrentDictionary2.GetOrAdd(TKey
key, Func2 valueFactory) +62
System.Data.Entity.Infrastructure.DefaultManifestTokenResolver.ResolveManifestToken(DbConnection
connection) +251
System.Data.Entity.Utilities.DbConnectionExtensions.GetProviderInfo(DbConnection
connection, DbProviderManifest& providerManifest) +56
System.Data.Entity.DbModelBuilder.Build(DbConnection
providerConnection) +43
System.Data.Entity.Internal.LazyInternalContext.CreateModel(LazyInternalContext
internalContext) +62
System.Data.Entity.Internal.RetryLazy2.GetValue(TInput input) +123
System.Data.Entity.Internal.LazyInternalContext.InitializeContext()
+627 System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type
entityType) +18
System.Data.Entity.Internal.Linq.InternalSet1.Initialize() +53
System.Data.Entity.Internal.Linq.InternalSet1.get_InternalContext()
+15 System.Data.Entity.Infrastructure.DbQuery1.System.Linq.IQueryable.get_Provider()
+38 System.Linq.Queryable.Where(IQueryable1 source, Expression1 predicate) +83
Saleboat.Logic.MeetingLogic.CheckMeetingFilter.OnActionExecuting(ActionExecutingContext
filterContext) in C:\Users\Michael\Documents\Visual Studio
2013\Projects\Saleboat\project-saleboat\Saleboat\Logic\MeetingLogic\CheckMeetingFilter.cs:22
System.Web.Mvc.Async.AsyncInvocationWithFilters.InvokeActionMethodFilterAsynchronouslyRecursive(Int32
filterIndex) +176
System.Web.Mvc.Async.AsyncInvocationWithFilters.InvokeActionMethodFilterAsynchronouslyRecursive(Int32
filterIndex) +644
System.Web.Mvc.Async.<>c__DisplayClass33.<BeginInvokeActionMethodWithFilters>b__31(AsyncCallback
asyncCallback, Object asyncState) +58
System.Web.Mvc.Async.WrappedAsyncResult1.CallBeginDelegate(AsyncCallback
callback, Object callbackState) +14
System.Web.Mvc.Async.WrappedAsyncResultBase1.Begin(AsyncCallback
callback, Object state, Int32 timeout) +128
System.Web.Mvc.Async.AsyncControllerActionInvoker.BeginInvokeActionMethodWithFilters(ControllerContext
controllerContext, IList1 filters, ActionDescriptor actionDescriptor,
IDictionary2 parameters, AsyncCallback callback, Object state) +197
System.Web.Mvc.Async.<>c__DisplayClass21.<BeginInvokeAction>b__19(AsyncCallback
asyncCallback, Object asyncState) +743
System.Web.Mvc.Async.WrappedAsyncResult1.CallBeginDelegate(AsyncCallback
callback, Object callbackState) +14
System.Web.Mvc.Async.WrappedAsyncResultBase1.Begin(AsyncCallback
callback, Object state, Int32 timeout) +128
System.Web.Mvc.Async.AsyncControllerActionInvoker.BeginInvokeAction(ControllerContext
controllerContext, String actionName, AsyncCallback callback, Object
state) +343
System.Web.Mvc.Controller.<BeginExecuteCore>b__1c(AsyncCallback
asyncCallback, Object asyncState, ExecuteCoreState innerState) +25
System.Web.Mvc.Async.WrappedAsyncVoid1.CallBeginDelegate(AsyncCallback
callback, Object callbackState) +30
System.Web.Mvc.Async.WrappedAsyncResultBase1.Begin(AsyncCallback
callback, Object state, Int32 timeout) +128
System.Web.Mvc.Controller.BeginExecuteCore(AsyncCallback callback,
Object state) +465
System.Web.Mvc.Controller.<BeginExecute>b__14(AsyncCallback
asyncCallback, Object callbackState, Controller controller) +18
System.Web.Mvc.Async.WrappedAsyncVoid1.CallBeginDelegate(AsyncCallback
callback, Object callbackState) +20
System.Web.Mvc.Async.WrappedAsyncResultBase1.Begin(AsyncCallback
callback, Object state, Int32 timeout) +128
System.Web.Mvc.Controller.BeginExecute(RequestContext requestContext,
AsyncCallback callback, Object state) +374
System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.BeginExecute(RequestContext
requestContext, AsyncCallback callback, Object state) +16
System.Web.Mvc.MvcHandler.<BeginProcessRequest>b__4(AsyncCallback
asyncCallback, Object asyncState, ProcessRequestState innerState) +52
System.Web.Mvc.Async.WrappedAsyncVoid1.CallBeginDelegate(AsyncCallback
callback, Object callbackState) +30
System.Web.Mvc.Async.WrappedAsyncResultBase`1.Begin(AsyncCallback
callback, Object state, Int32 timeout) +128
System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase
httpContext, AsyncCallback callback, Object state) +384
System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext,
AsyncCallback callback, Object state) +48
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext
context, AsyncCallback cb, Object extraData) +16
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
+103 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155

Answer 1

With Npgsql 3.1.5 try to use "Trust Server Certificate=true" in connection string.
Example connection string:
Server=[servername];Port=[port];User Id=[username];Password=[password];Database=[databasename];sslmode=Require;Trust Server Certificate=true