Seed data in a database using .NET Aspire

2025-05-27

In this article, you learn how to configure .NET Aspire projects to seed data in a database during app startup. .NET Aspire enables you to seed data using database scripts or Entity Framework Core (EF Core) for common platforms such as SQL Server, PostgreSQL, and MySQL.

When to seed data

Seeding data pre-populates database tables with rows of data so they're ready for testing your app. You may want to seed data for the following scenarios:

You want to develop and test different features of your app manually against a meaningful set of data, such as a product catalog or a list of customers.
You want to run test suites to verify that features behave correctly with a given set of data.

Manually seeding data is tedious and time consuming, so you should automate the process whenever possible. You can seed your database either by running database scripts for .NET Aspire projects during startup or by using tools like EF Core, which handles many underlying concerns for you.

Understand containerized databases

By default, .NET Aspire database integrations rely on containerized databases, which create the following challenges when trying to seed data:

By default, .NET Aspire destroys and recreates containers every time the app restarts, which means you have to re-seed your database on each run.
Depending on your selected database technology, the new container instance may or may not create a default database, which means you might also have to create the database itself.
Even if a default database exists, it most likely won't have the desired name or schema for your specific app.

.NET Aspire enables you to resolve these challenges using volumes, bind mounts, and a few configurations to seed data effectively.

Tip

Container hosts like Docker and Podman support volumes and bind mounts, both of which provide locations for data that persist when a container restarts. Volumes are the recommended solution, because they offer better performance, portability, and security. The container host creates and remains in control of volumes. Each volume can store data for multiple containers. Bind mounts have relatively limited functionality in comparison but enable you to access the data from the host machine.

Note

Visit the Database Container Sample App to view the full project and file structure for each database option.

Seed data using SQL scripts

In .NET Aspire 9.2, the recommended method for executing database seeding scripts depends on the database server you use:

In .NET Aspire 9.2 and later versions, you can use the WithCreationScript method to ensure a T-SQL script is run when the database is created. Add SQL code to this script that creates and populates the database, the necessary tables, and other database objects.

The following code is an example T-SQL script that creates and populates an address book database:

-- SQL Server init script

-- Create the AddressBook database
IF NOT EXISTS (SELECT * FROM sys.databases WHERE name = N'AddressBook')
BEGIN
  CREATE DATABASE AddressBook;
END;
GO

USE AddressBook;
GO

-- Create the Contacts table
IF OBJECT_ID(N'Contacts', N'U') IS NULL
BEGIN
    CREATE TABLE Contacts
    (
        Id        INT PRIMARY KEY IDENTITY(1,1) ,
        FirstName VARCHAR(255) NOT NULL,
        LastName  VARCHAR(255) NOT NULL,
        Email     VARCHAR(255) NULL,
        Phone     VARCHAR(255) NULL
    );
END;
GO

-- Ensure that either the Email or Phone column is populated
IF OBJECT_ID(N'chk_Contacts_Email_Phone', N'C') IS NULL
BEGIN
    ALTER TABLE Contacts
    ADD CONSTRAINT chk_Contacts_Email_Phone CHECK
    (
        Email IS NOT NULL OR Phone IS NOT NULL
    );
END;
GO

-- Insert some sample data into the Contacts table
IF (SELECT COUNT(*) FROM Contacts) = 0
BEGIN
    INSERT INTO Contacts (FirstName, LastName, Email, Phone)
    VALUES
        ('John', 'Doe', 'john.doe@example.com', '555-123-4567'),
        ('Jane', 'Doe', 'jane.doe@example.com', '555-234-5678');
END;
GO

You must ensure that this script is copied to the app host's output directory, so that .NET Aspire can execute it. Add the following XML to your .csproj file:

<ItemGroup>
  <None Include="..\DatabaseContainers.ApiService\data\sqlserver\init.sql" Link="init.sql">
    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
  </None>
</ItemGroup>

Adjust the Include parameter to match the path to your SQL script in the project.

Next, in the app host's AppHost.cs (or Program.cs) file, create the database and run the creation script:

var sqlserver = builder.AddSqlServer("sqlserver")
    // Configure the container to store data in a volume so that it persists across instances.
    .WithDataVolume()
    // Keep the container running between app host sessions.
    .WithLifetime(ContainerLifetime.Persistent);

// Add the database to the application model so that it can be referenced by other resources.
var initScriptPath = Path.Join(Path.GetDirectoryName(typeof(Program).Assembly.Location), "init.sql");
var addressBookDb = sqlserver.AddDatabase("AddressBook")
    .WithCreationScript(File.ReadAllText(initScriptPath));

This code:

Create a SQL Server container by calling builder.AddSqlServer().
Ensures that data is persisted across debugging sessions by calling WithDataVolume() and WithLifetime(ContainerLifetime.Persistent).
Obtains the path to the T-SQL script in the output folder.
Calls WithCreationScript() to create and seed the database.

In .NET Aspire 9.2, the WithCreationScript() method isn't supported for the PostgreSQL integration. Instead, you must use a bind mount and deploy the setup SQL script to it, so that the data is seeded when the container initializes the database.

The following code is an example PostgreSQL script that creates and populates a to do list database:

-- Postgres init script

-- Create the Todos table
CREATE TABLE IF NOT EXISTS Todos
(
    Id SERIAL PRIMARY KEY,
    Title text UNIQUE NOT NULL,
    IsComplete boolean NOT NULL DEFAULT false
);

-- Insert some sample data into the Todos table
INSERT INTO Todos (Title, IsComplete)
VALUES
    ('Give the dog a bath', false),
    ('Wash the dishes', false),
    ('Do the groceries', false)
ON CONFLICT DO NOTHING;

In the app host's AppHost.cs (or Program.cs) file, create the database and mount the folder that contains the SQL script as a bind mount:

// PostgreSQL container is configured with an auto-generated password by default
// and supports setting the default database name via an environment variable & running *.sql/*.sh scripts in a bind mount.
var todosDbName = "Todos";

var postgres = builder.AddPostgres("postgres")
    // Set the name of the default database to auto-create on container startup.
    .WithEnvironment("POSTGRES_DB", todosDbName)
    // Mount the SQL scripts directory into the container so that the init scripts run.
    .WithBindMount("../DatabaseContainers.ApiService/data/postgres", "/docker-entrypoint-initdb.d")
    // Configure the container to store data in a volume so that it persists across instances.
    .WithDataVolume()
    .WithPgWeb()
    // Keep the container running between app host sessions.
    .WithLifetime(ContainerLifetime.Persistent);

// Add the default database to the application model so that it can be referenced by other resources.
var todosDb = postgres.AddDatabase(todosDbName);

In .NET Aspire 9.2, the WithCreationScript() method isn't supported for the MySQL integration. Instead, you must use a bind mount and deploy the setup SQL script to it, so that the data is seeded when the container initializes the database.

The following code is an example MySQL script that creates and populates a product catalog database:

-- MySql init script

-- NOTE: MySql database and table names are case-sensitive on non-Windows platforms!
--       Column names are always case-insensitive.

-- Create the Catalog table
CREATE TABLE IF NOT EXISTS `catalog`
(
    `id` int(11) NOT NULL AUTO_INCREMENT,
    `name` varchar(255) NOT NULL,
    `description` varchar(255) NOT NULL,
    `price` DECIMAL(18,2) NOT NULL,
    PRIMARY KEY (`id`)
);

-- Insert some sample data into the Catalog table only if the table is empty
INSERT INTO catalog (name, description, price)
SELECT *
FROM (
        SELECT '.NET Bot Black Hoodie', 'This hoodie will keep you warm while looking cool and representing .NET!', 19.5 UNION ALL
        SELECT '.NET Black & White Mug', 'The perfect place to keep your favorite beverage while you code.', 8.5 UNION ALL
        SELECT 'Prism White T-Shirt', "It's a t-shirt, it's white, and it can be yours.", 12
    ) data
-- This clause ensures the rows are only inserted if the table is empty
WHERE NOT EXISTS (SELECT NULL FROM catalog)

In the app host's AppHost.cs (or Program.cs) file, create the database and mount the folder that contains the SQL script as a bind mount:

// MySql container is configured with an auto-generated password by default
// and supports setting the default database name via an environment variable & running *.sql/*.sh scripts in a bind mount.
var catalogDbName = "catalog"; // MySql database & table names are case-sensitive on non-Windows.

var mysql = builder.AddMySql("mysql")
    // Set the name of the database to auto-create on container startup.
    .WithEnvironment("MYSQL_DATABASE", catalogDbName)
    // Mount the SQL scripts directory into the container so that the init scripts run.
    .WithBindMount("../DatabaseContainers.ApiService/data/mysql", "/docker-entrypoint-initdb.d")
    // Configure the container to store data in a volume so that it persists across instances.
    .WithDataVolume()
    // Keep the container running between app host sessions.
    .WithLifetime(ContainerLifetime.Persistent);

// Add the database to the application model so that it can be referenced by other resources.
var catalogDb = mysql.AddDatabase(catalogDbName);

Seed data using EF Core

You can also seed data in .NET Aspire projects using EF Core by explicitly running migrations during startup. EF Core handles underlying database connections and schema creation for you, which eliminates the need to use volumes or run SQL scripts during container startup.

Important

These types of configurations should only be done during development, so make sure to add a conditional that checks your current environment context.

Add the following code to the _Program.cs file of your API Service project.

// Register DbContext class
builder.AddSqlServerDbContext<TicketContext>("sqldata");

var app = builder.Build();

app.MapDefaultEndpoints();

if (app.Environment.IsDevelopment())
{
    // Retrieve an instance of the DbContext class and manually run migrations during startup
    using (var scope = app.Services.CreateScope())
    {
        var context = scope.ServiceProvider.GetRequiredService<TicketContext>();
        context.Database.Migrate();
    }
}

// Register DbContext class
builder.AddNpgsqlDbContext<TicketContext>("sqldata");

var app = builder.Build();

app.MapDefaultEndpoints();

if (app.Environment.IsDevelopment())
{
    // Retrieve an instance of the DbContext class and manually run migrations during startup
    using (var scope = app.Services.CreateScope())
    {
        var context = scope.ServiceProvider.GetRequiredService<TicketContext>();
        context.Database.Migrate();
    }
}

// Register DbContext class
builder.AddMySqlDataSource<TicketContext>("sqldata");

var app = builder.Build();

app.MapDefaultEndpoints();

if (app.Environment.IsDevelopment())
{
    // Retrieve an instance of the DbContext class and manually run migrations during startup
    using (var scope = app.Services.CreateScope())
    {
        var context = scope.ServiceProvider.GetRequiredService<TicketContext>();
        context.Database.Migrate();
    }
}

Next steps

Database seeding is useful in a variety of app development scenarios. Try combining these techniques with the resource implementations demonstrated in the following tutorials:

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