Connection strings

Connection strings

Every container implements IConnectionStringProvider, so you can ask any container for its connection string without knowing the module type:

IContainer container = new PostgreSqlBuilder().Build();
await container.StartAsync();

string connectionString = container.GetConnectionString();            // ConnectionMode.Host
string same = container.GetConnectionString(ConnectionMode.Host);     // explicit

Connection modes

ConnectionMode describes how the connection string targets the container:

Mode	Meaning	Support
Host	Test host → container, using the mapped host port (127.0.0.1:{port}).	✅ both backends
Container	Container → container, using the container network.	❌ not supported yet

ConnectionMode.Container throws ConnectionStringModeNotSupportedException. Neither backend supports container-to-container networking today: WSLC has no managed networks or inter-container DNS, and the Docker backend does not attach containers to a shared network. Multi-container wiring is deliberately deferred (see Networking).

How it works

A module’s builder registers a connection string provider that delegates to the module’s own GetConnectionString():

sealed class PostgreSqlConnectionStringProvider
    : ContainerConnectionStringProvider<PostgreSqlContainer, PostgreSqlConfiguration>
{
    protected override string GetHostConnectionString() => Container.GetConnectionString();
}

ContainerConnectionStringProvider<TContainer, TConfiguration> is the base class: Configure runs once, after the container has started (so runtime-assigned ports are available), and dispatches GetConnectionString(ConnectionMode) to GetHostConnectionString() / GetContainerConnectionString(). The named overload (GetConnectionString(name, mode)) exists for modules with several endpoints; the base throws ConnectionStringNameNotSupportedException unless a provider overrides it.

Custom provider

Override the connection string a container exposes with WithConnectionStringProvider:

sealed class ReadOnlyPostgreSql : ContainerConnectionStringProvider<PostgreSqlContainer, PostgreSqlConfiguration>
{
    protected override string GetHostConnectionString() => $"{Container.GetConnectionString()};ApplicationName=readonly";
}

var postgres = new PostgreSqlBuilder()
    .WithConnectionStringProvider(new ReadOnlyPostgreSql())
    .Build();

Providers that produce an empty connection string throw ConnectionStringNotAvailableException, and a provider used before Configure throws ConnectionStringProviderNotConfiguredException.

Module reference

See Modules for each module’s default connection string and any extra endpoint accessors.