The specified LocalDb instance does not exist

Question

I've been using a localDB named 'Projects' for a while now. This is the same database that is created by default ASP.NET MVC 5 project. However, suddenly it stopped and I'm not able to connect to it nor restart it using

SqlLocalDb start Projects

I get

The specified LocalDB instance does not exist.

I see the folder in

C:\Users\[My UserName]\AppData\Local\Microsoft\Microsoft SQL Server Local DB\Instances\Projects

also, I have v11.0 in

C:\Users\[My UserName]\AppData\Local\Microsoft\Microsoft SQL Server Local DB\Instances\v11.0

I'm able to connect to v11.

What else can I try to reconnect to it?

The connection string is

 <add name="DefaultConnection"  connectionString="Data Source=(localdb)\Projects;Initial Catalog=master;Integrated Security=True;Connect Timeout=30;Encrypt=False;TrustServerCertificate=False" providerName="System.Data.SqlClient" />

Edit

I tried Attaching the Db file to the connection string

AttachDbFileName=C:\Users\[My UserName]\AppData\Local\Microsoft\Microsoft SQL Server Local DB\Instances\Projects\master.mdf;

However, I'm still not able to connect

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. The specified LocalDB instance
does not exist.)

Answer 1

Seems like (localdb)\Projects instance got deleted. You can either use (localdb)\v11.0 or recreate Projects instance using SqlLocalDB utility

sqllocaldb c Projects 11.0

Command line explained

• c - is for "create"
• "Projects - is the instance name
• 11.0 is the version

Answer 2

In my case the Projects instance was already there, actually after invoking this in the command line:

sqllocaldb i

A list of all the instances shows up, mine were:

• MSSQLLocalDB
• Projects
• ProjectsV12
• v11.0

The connection string in my Web.Config had Data Source=(LocalDb)\v11.0 by default, so I supposed the instance should actually be v11.0 and not Projects. By executing sqllocaldb i v11.0:

Name: v11.0

Version: 11.0.3000.0

...

Auto-create: Yes

State: Stopped

...

And by starting the instance with sqllocaldb s v11.0 the State was changed to Running, but even while these instances were all running, the exception was still being thrown.

I figured out later that the name of the instance must be the one that shows up when you invoke Update-Database -Verbose in the Package Manager Console, in mine this showed up:

Target database is: 'Videos.Models.VideoDb' (DataSource: (localdb)**v12.0**, Provider: System.Data.SqlClient, Origin: Convention).

Therefore I just needed to create v12.0 instance with sqllocaldb c v12.0 12.0 and adjust the Web.Config to this name. After doing this the update was successful.