MongoDB.DbContext

A DB context implementation for MongoDB.

The DB context implementation is very heavily inspired by the EntityFramework Core DbContext infrastructure. The options configuration works the same. The database options can be set when configuring the context, or agail later (and maybe altered) when new instances of the context are created.

The context services are registered as scoped automatically. Every context will get the MongoDB driver services (IMongoDatabase, IMongoClient) from an interner service provider which will have those services registered as singleton instances. This cache of internal service providers uses the conenction string, str database name and the context options type as key, so changing the database name for a context at runtime (by overriding OnConfiguring) will result in a new internal service provider with the corresponding MongoDB singleton services.

Usage

To add a MongoDbContext one uses the AddMongoDbContext extension method. There are several ways to configure one or multiple contexts.

Configuration without custom context class

To get started quickly, one can simply use the MongoDbContext class and configure the database by passing an options builder action to AddMongoDbContext. This way you have no possibility to further configure the context at runtime.

services.AddMongoDbContext<MongoDbContext>(builder =>
{
	builder.UseDatabase("mongodb://localhost:27017", "test");
});

Configuration with custom context class

If you need more control ove the context configuration or need to add multiple different contexts, you need to dervice you context class from MongoDbContext

services.AddMongoDbContext<SampleContext>(builder =>
{
	builder.UseDatabase("mongodb://localhost:27017", "test");
});

public sealed class SampleContext : MongoDbContext
{
	public SampleContext(MongoDbContextOptions options)
		: base(options)
	{
	}

	/// <inheritdoc />
	protected override void OnConfiguring(MongoDbContextOptionsBuilder builder)
	{
		builder.UseDatabase("mongodb://localhost:27017", "other");
	}
}

The OnConfiguring method is called everytime a new instance of the context is created, so it is possible to change the connection settings for the context based on runtime information.

Configuring multiple different context classes

If you need to add several contexts you need to inject the generic version of the MongoDbContextOptions to allow the correct options be created. There will be an exception thrown if you don't do it.

services.AddMongoDbContext<SampleContextOne>(builder =>
{
	builder.UseDatabase("mongodb://localhost:27017", "one");
});

services.AddMongoDbContext<SampleContextTwo>(builder =>
{
	builder.UseDatabase("mongodb://localhost:27017", "two");
});

public sealed class SampleContextOne : MongoDbContext
{
	public SampleContext(MongoDbContextOptions<SampleContextOne> options)
		: base(options)
	{
	}
}

public sealed class SampleContextTwo : MongoDbContext
{
	public SampleContext(MongoDbContextOptions<SampleContextTwo> options)
		: base(options)
	{
	}
}

Configuring telemetry information

To expose telemetry information via System.Diagnostics just enable it in the MongoDbContextOptions. If you like to integrate this telemetry into OpenTelemetry just add a source with the name MongoDB.Driver.Core.Extensions.DiagnosticSources.

services.AddMongoDbContext<SampleContext>(builder =>
{
	builder
		.UseDatabase("mongodb://localhost:27017", "test")
		.EnableTelemetry();
});

References

EntityFramework Core

MongoDB.Driver.Core.Extensions.DiagnosticSources