Hang in System.Data.Entity.DbSet.Add() - entity-framework

Question

I am following the Create an OData v4 Endpoint Using ASP.NET Web API 2.2 sample, and the Post() method implementation looks like this:
public async Task<IHttpActionResult> Post(Product product)
{
if (!ModelState.IsValid)
{
return BadRequest(ModelState);
}
db.Products.Add(product);
await db.SaveChangesAsync();
return Created(product);
}
However, when a Post request is received, Products.Add() hangs and never returns. No exception is thrown.
Under WinDBG I can see the following callstack:
System.Threading.Thread.Sleep
System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover
System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist
System.Data.SqlClient.SqlInternalConnectionTds..ctor
System.Data.SqlClient.SqlConnectionFactory.CreateConnection
System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection
System.Data.ProviderBase.DbConnectionPool.CreateObject
System.Data.ProviderBase.DbConnectionPool.UserCreateRequest
System.Data.ProviderBase.DbConnectionPool.TryGetConnection
System.Data.ProviderBase.DbConnectionPool.TryGetConnection
System.Data.ProviderBase.DbConnectionFactory.TryGetConnection
System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal
System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection
System.Data.SqlClient.SqlConnection.TryOpenInner
System.Runtime.InteropServices.SafeHandle.Dispose
System.Data.SqlClient.SqlConnection.TryOpen
System.Data.SqlClient.SqlConnection.Open
System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.Open
System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute
System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute
System.Data.Entity.SqlServer.SqlProviderServices.UsingConnection
System.Data.Entity.SqlServer.SqlProviderServices.UsingMasterConnection
System.Data.Entity.SqlServer.SqlProviderServices.GetDbProviderManifestToken
System.Data.Entity.Core.Common.DbProviderServices.GetProviderManifestToken
System.Data.Entity.Utilities.DbProviderServicesExtensions.GetProviderManifestTokenChecked
System.Data.Entity.Infrastructure.DefaultManifestTokenResolver.ResolveManifestToken
System.Data.Entity.Utilities.DbConnectionExtensions.GetProviderInfo
System.Data.Entity.DbModelBuilder.Build
System.Data.Entity.Internal.LazyInternalContext.CreateModel
System.Data.Entity.Internal.LazyInternalContext.InitializeContext
System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType
System.Data.Entity.DbSet.Add
ProductService.Controllers.ProductsController.Post
I am using EntityFramework 6.1.3.
If the Add() method is the one creating the connection with the database, should it be an *Async() method?
Update:
After porting the code from ASP.NET to Console Application, I caught the following exception:
An unhandled exception of type 'System.Data.SqlClient.SqlException' occurred in EntityFramework.dll
Additional information: 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.)

Answer 1

The problem is that the tutorial connection string is not valid anymore for Visual Studio 2015; Data Source=(localdb)\v11.0 needs to be replaced with Data Source=(localdb)\mssqllocaldb.
I.e.:
<add
name="ProductsContext"
connectionString="Data Source=(localdb)\mssqllocaldb;
Initial Catalog=ProductsContext; Integrated Security=True;
MultipleActiveResultSets=True;
AttachDbFilename=|DataDirectory|ProductsContext.mdf"
providerName="System.Data.SqlClient" />