Hosting an web API on localhost with (LocalDb) connectionstring cannot connect - iis

Question

I have setup my web api application on my local IIS (Windows 10). Then I've also been into my host file and set it up as:
api.domain.com 127.0.0.1
When I try to make a POST using Postman to:
http://api.api.domain.com/api/account/register
Then I get the following error:
{
"Message": "An error has occurred.",
"ExceptionMessage": "A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 50 - Local Database Runtime error occurred. Cannot create an automatic instance. See the Windows Application event log for error details.\r\n)",
"ExceptionType": "System.Data.SqlClient.SqlException",
"StackTrace": " at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)\r\n at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)\r\n at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)\r\n at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)\r\n at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)\r\n at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)\r\n at System.Data.SqlClient.SqlConnection.Open()\r\n at System.Data.Entity.Infrastructure.Interception.InternalDispatcher`1.Dispatch[TTarget,TInterceptionContext](TTarget target, Action`2 operation, TInterceptionContext interceptionContext, Action`3 executing, Action`3 executed)\r\n at System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.Open(DbConnection connection, DbInterceptionContext interceptionContext)\r\n at System.Data.Entity.SqlServer.SqlProviderServices.<>c__DisplayClass33.<UsingConnection>b__32()\r\n at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.<>c__DisplayClass1.<Execute>b__0()\r\n at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func`1 operation)\r\n at System.Data.Entity.SqlServer.SqlProviderServices.UsingMasterConnection(DbConnection sqlConnection, Action`1 act)\r\n at System.Data.Entity.SqlServer.SqlProviderServices.CreateDatabaseFromScript(Nullable`1 commandTimeout, DbConnection sqlConnection, String createDatabaseScript)\r\n at System.Data.Entity.SqlServer.SqlProviderServices.DbCreateDatabase(DbConnection connection, Nullable`1 commandTimeout, StoreItemCollection storeItemCollection)\r\n at System.Data.Entity.Migrations.Utilities.DatabaseCreator.Create(DbConnection connection)\r\n at System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists(Action mustSucceedToKeepDatabase)\r\n at System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration)\r\n at System.Data.Entity.Internal.DatabaseCreator.CreateDatabase(InternalContext internalContext, Func`3 createMigrator, ObjectContext objectContext)\r\n at System.Data.Entity.Database.Create(DatabaseExistenceState existenceState)\r\n at System.Data.Entity.CreateDatabaseIfNotExists`1.InitializeDatabase(TContext context)\r\n at System.Data.Entity.Internal.InternalContext.PerformInitializationAction(Action action)\r\n at System.Data.Entity.Internal.InternalContext.PerformDatabaseInitialization()\r\n at System.Data.Entity.Internal.RetryAction`1.PerformAction(TInput input)\r\n at System.Data.Entity.Internal.LazyInternalContext.InitializeDatabaseAction(Action`1 action)\r\n at System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType)\r\n at System.Data.Entity.Internal.Linq.InternalSet`1.Initialize()\r\n at System.Data.Entity.Internal.Linq.InternalSet`1.get_InternalContext()\r\n at System.Data.Entity.Infrastructure.DbQuery`1.System.Linq.IQueryable.get_Provider()\r\n at System.Data.Entity.QueryableExtensions.FirstOrDefaultAsync[TSource](IQueryable`1 source, Expression`1 predicate, CancellationToken cancellationToken)\r\n at System.Data.Entity.QueryableExtensions.FirstOrDefaultAsync[TSource](IQueryable`1 source, Expression`1 predicate)\r\n at Microsoft.AspNet.Identity.EntityFramework.UserStore`6.<GetUserAggregateAsync>d__6c.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.AspNet.Identity.TaskExtensions.CultureAwaiter`1.GetResult()\r\n at Microsoft.AspNet.Identity.UserValidator`2.<ValidateUserName>d__4.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.AspNet.Identity.UserValidator`2.<ValidateAsync>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.AspNet.Identity.UserManager`2.<CreateAsync>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Microsoft.AspNet.Identity.UserManager`2.<CreateAsync>d__d.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at Asano.Websites.Api.Controllers.AccountController.<Register>d__20.MoveNext() in C:\\Users\\Lars Holdgaard\\Documents\\Git\\Eesy\\Eesy\\Eesy.Websites.Api\\Controllers\\AccountController.cs:line 339\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Threading.Tasks.TaskHelpersExtensions.<CastToObject>d__3`1.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.AuthenticationFilterResult.<ExecuteAsync>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()"
}
However, if I run the application inside VisualStudio it works fine.
What is the reason for this, and how is this usually fixed? :-)
EDITS:
My connectionstring is:
<add name="AsanoWebsitesApiContext" connectionString="Server=(LocalDb)\MSSQLLocalDB;Database=Eesy;Trusted_Connection=True;" providerName="System.Data.SqlClient" />
Which again works in Visual Studio, but not on localhost.

Answer 1

The symptom:
A network-related or instance-specific error occurred while
establishing a connection to SQL Server. The server was not found or
was not accessible. Verify that the instance name is correct and that
SQL Server is configured to allow remote connections.
There are plenty of posts around the web with this issue, which can be overwhelming, but from my experience, this problem can be caused by 3 different settings.
Remote connections are not allowed in your MS-SQL database.
TCP/IP is not allowed in your MSSQLSERVER protocol settings.
The database' TCP/UDP ports are blocked.
Let's go through all of these problems one by one in the steps below:
Open MS-SQL management studio and, after connecting to your DB server, right-click the server (not the database), and choose properties.
Click on the Connections section and ensure that Allow remote connections to this server is checked. If it's not, check it, and check if this solves the problem.
If not checked or problem still exists, close the MS-SQL management studio, and open the SQL Server Configuration Manager.
Unfold the node SQL Server Network Configuration and select Protocols for MSSQL-Server.
Make sure that TCP/IP is enabled and try again.
If problem still exists, right click TCP/IP and select Properties.
See which port number is used (default is 1433).
Open the Control Panel and navigate to Windows Firewall.
Click on Advanced Settings on the left hand side and you should see the Windows Firewall with Advanced Security. Select the Inboud Rules on the left hand side and click on New Rule…
You can create a rule to allow inbound traffic on Port 1433 (or the port number from step (7) for TCP/IP. Choose Port > TCP > and enter the port number from step (7) > Choose Allow the connection > Choose Domain > Give the rule a name, and you're done.
Repeat step 10, this time for UDP.