Cannot connect to Microsoft SQL Server database after creating it ("The system cannot find the file specified")

Question

I have a script that preps an environment for a test run which requires a database connection (creates a few tables writes a few values etc.)

I have a PowerShell script that creates the DB_NAME via

& sqllocaldb create DB_NAME
& sqllocaldb start DB_NAME
& sqllocaldb info DB_NAME

The output is:

LocalDB instance "DB_NAME" created with version 13.1.4001.0.
LocalDB instance "DB_NAME" started.

Name:               DB_NAME
Version:            13.1.4001.0

Shared name:        

Owner:              fv-az604\VssAdministrator
Auto-create:        No
State:              Running

Last start time:    11/7/2019 11:47:43 PM

Instance pipe name: np:\\.\pipe\LOCALDB#24C8D765\tsql\query

The connection is performed via the following code

using (SqlCommand cmd = new SqlCommand(sql))
{
    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        cmd.Connection = connection;
        cmd.Connection.Open();
        cmd.ExecuteNonQuery();
    }
}

where the connection string looks like this:

Application Name=MyApp;Connect Timeout=60;Data Source=localhost;Initial Catalog=master;Integrated Security=sspi;Connection Reset=false;Min Pool Size=1;Max Pool Size=200;Pooling=true;MultipleActiveResultSets=true;Enlist=false

Database name: DB_NAME

The full stack trace is:

[Error]: 
Type: System.ComponentModel.Win32Exception
Message: The system cannot find the file specified
Source: 
Stack:

Type: System.Data.SqlClient.SqlException
Message: 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: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
Source: .Net SqlClient Data ProviderHelpLink.ProdName: Microsoft SQL Server
HelpLink.EvtSrc: MSSQLServer
HelpLink.EvtID: 2
HelpLink.BaseHelpUrl: http://go.microsoft.com/fwlink
HelpLink.LinkId: 20476

Stack:
   at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, DbConnectionPool pool, String accessToken, Boolean applyTransientFaultHandling, SqlAuthenticationProviderManager sqlAuthProviderManager)
   at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
   at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.Open()
   at MyClass.MyFuncABC(String connectionString, String databaseName) in D:\a\1\s\App\MyClass.cs:line 333
   at MyClass.MyFuncAB() in D:\a\1\s\App\MyClass.cs:line 444
   at MyClass.MyFuncA() in D:\a\1\s\App\MyClass.cs:line 555
   at App.Main(String[] args) in D:\a\1\s\App\Main.cs:line 1337

Answer 1

The first error message about missing file is just mud in the water. The real one is the second one, which is well-known to about every SQL Server DBA:

Message: 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: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)

As the message says, connection cannot be made into SQL Server. The client library tries to connect via TCP/IP, Shared Memory and Named Pipes. Since pipes is the last option, and it fails too, the error contains message from pipes.

LocalDB has it's own, quite peculiar syntax, for connection strings. The one you've used is to connect into a real SQL Server.

Maybe something like

Server=np:\\.\pipe\LOCALDB#24C8D765\tsql\query

would work better. Also, find out your localdb's instance name and try something like

Server=(localdb)\MyInstance;Integrated Security=true;