ASP.NET Core 9 Web API — LocalDB .mdf file — Need Help Making It Work

Mohammad Ahmad

I'm building an ASP.NET Core 9 Web API project, and I want the whole application to be completely self-contained — no need for any external database setup, no SQL Server Management Studio (SSMS), just run the app and everything works.

I'm using a local SQL Server .mdf file stored inside the project folder, and I'm trying to connect to it using LocalDB.

What I did

Added the .mdf and .ldf files inside a Database/ folder in the project root
I am using SQL Server with ADO.NET on it I copied the .mdf file from my SQL Server (it works on SQL Server)
Used this connection string in appsettings.json:
```
"ConnectionStrings": 
{
    "DefaultConnection": "Data Source=(LocalDB)\\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\\Database\\BankAPI.mdf;Integrated Security=True;Connect Timeout=30" 
}
```
I'm building an ASP.NET Core 9 Web API project, and I want the whole application to be completely self-contained — no need for any external database setup, no SQL Server Management Studio (SSMS), just run the app and everything works.

I'm using a local SQL Server .mdf file stored inside the project folder, and I'm trying to connect to it using LocalDB.

What I did
Added the .mdf and .ldf files inside a Database/ folder in the project root
I am using SQL Server with ADO.NET on it I copied the .mdf file from my SQL Server (it works on SQL Server)

Used this connection string in appsettings.json:

"ConnectionStrings": 
{
    "DefaultConnection": "Data Source=(LocalDB)\\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\\Database\\BankAPI.mdf;Integrated Security=True;Connect Timeout=30" 
}

What I need help with:
Is this the correct way to make the .mdf file work?
Do I need to add or configure anything else to ensure it works on any machine without needing SSMS or SQL Server setup?
Any tips from someone who’s done a similar setup?
Does anyone have a recurse to learn and see how to do it will be very helpful
Am I doing things right any way?

My project folder structure looks like this:

Bank Project/
+-- API Layer/
¦   +-- Program.cs
¦   +-- appsettings.json
+-- Business Logic Layer/
+-- Data Access Layer/
+-- Database/
¦   +-- BankAPI.mdf
¦   +-- BankAPI_log.ldf

2 Replies

Know the answer? Post it — somebody with the same question will find it here.

Tuhin Paul1y ago
Your approach is valid, but there are a few things to consider for a truly portable solution:

What You're Doing Correctly
- Using LocalDB (MSSQLLocalDB) which is a lightweight version of SQL Server
- Storing the database files within your project structure
- Using |DataDirectory| token which points to your app's root directory
1. Database File Properties

Make sure your .mdf and .ldf files have these properties in Visual Studio:
- Build Action: "Content"
- Copy to Output Directory: "Copy if newer"
This ensures the files are included when you build/publish the application.

2. Connection String Adjustment

Modify your connection string to be more robust:
```
"ConnectionStrings": {
    "DefaultConnection": "Data Source=(LocalDB)\\MSSQLLocalDB;AttachDbFilename={AppDir}\\Database\\BankAPI.mdf;Integrated Security=True;Connect Timeout=30;"
}
```
Then in your Program.cs, replace {AppDir} with the actual application directory:
```
var builder = WebApplication.CreateBuilder(args);

// Get the application base directory
var appDir = AppContext.BaseDirectory;

// Replace {AppDir} in connection string
var connectionString = builder.Configuration.GetConnectionString("DefaultConnection")
    ?.Replace("{AppDir}", appDir);

// Register your DbContext with the updated connection string
builder.Services.AddDbContext(options => 
    options.UseSqlServer(connectionString));
```
If you want even more portability (no LocalDB requirement), consider SQLite.
0
Prasad Raveendran1y ago
refer the below URLs

https://learn.microsoft.com/en-us/sql/database-engine/configure-windows/sql-server-express-localdb?view=sql-server-ver17

https://learn.microsoft.com/en-us/ef/core/

You're doing it right if:
- LocalDB is installed on the machine
- DataDirectory is set
- .mdf is marked PreserveNewest
- You don't need multi-user access or migrations
If you want more portability, consider:
- SQLite (zero setup) if relational DB is needed
- EF Core + In-Memory DB for dev/test
0

ASP.NET Core 9 Web API — LocalDB .mdf file — Need Help Making It Work

What You're Doing Correctly

1. Database File Properties

2. Connection String Adjustment