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.NET Aspire Pomelo MySQL Entity Framework Component

  • Статья

In this article, you learn how to use the The .NET Aspire Pomelo MySQL Entity Framework Core component. The Aspire.Pomelo.EntityFrameworkCore.MySql library is used to register a System.Data.Entity.DbContext as a singleton in the DI container for connecting to MySQL databases. It also enables connection pooling, retries, health checks, logging and telemetry.

Get started

You need a MySQL database and connection string for accessing the database. To get started with the The .NET Aspire Pomelo MySQL Entity Framework Core component, install the Aspire.Pomelo.EntityFrameworkCore.MySql NuGet package.

dotnet add package Aspire.Pomelo.EntityFrameworkCore.MySql

For more information, see dotnet add package or Manage package dependencies in .NET applications.

Example usage

In the Program.cs file of your component-consuming project, call the AddMySqlDbContext extension to register a System.Data.Entity.DbContext for use via the dependency injection container.

builder.AddMySqlDbContext<MyDbContext>("mysqldb");

You can then retrieve the DbContext instance using dependency injection. For example, to retrieve the client from a service:

public class ExampleService(MyDbContext context)
{
    // Use context...
}

You might also need to configure specific options of your MySQL connection, or register a DbContext in other ways. In this case call the EnrichMySqlDbContext extension method, for example:

var connectionString = builder.Configuration.GetConnectionString("mysqldb");

builder.Services.AddDbContextPool<MyDbContext>(
    dbContextOptionsBuilder => dbContextOptionsBuilder.UseMySql(connectionString, serverVersion));
builder.EnrichMySqlDbContext<MyDbContext>();

App host usage

To model the MySql resource in the app host, install the Aspire.Hosting.MySql NuGet package.

dotnet add package Aspire.Hosting.MySql

In your app host project, register a MySql database and consume the connection using the following methods:

var mysql = builder.AddMySql("mysql");
var mysqldb = mysql.AddDatabase("mysqldb");

var myService = builder.AddProject<Projects.MyService>()
                       .WithReference(mysqldb);

Configuration

The .NET Aspire Pomelo MySQL Entity Framework Core component provides multiple options to configure the database connection based on the requirements and conventions of your project.

Use a connection string

When using a connection string from the ConnectionStrings configuration section, you can provide the name of the connection string when calling builder.AddMySqlDatabaseDbContext<TContext>():

builder.AddMySqlDatabaseDbContext<MyDbContext>("myConnection");

And then the connection string will be retrieved from the ConnectionStrings configuration section:

{
  "ConnectionStrings": {
    "myConnection": "Server=myserver;Database=mysqldb"
  }
}

The EnrichMySqlDbContext won't make use of the ConnectionStrings configuration section since it expects a DbContext to be registered at the point it is called.

See the MySqlConnector documentation for more information on how to format this connection string.

Use configuration providers

The .NET Aspire Pomelo MySQL Entity Framework Core component supports Microsoft.Extensions.Configuration. It loads the PomeloEntityFrameworkCoreMySqlSettings from configuration by using the Aspire:Pomelo:EntityFrameworkCore:MySql key.

The following example shows an appsettings.json that configures some of the available options:

{
  "Aspire": {
    "Pomelo": {
      "EntityFrameworkCore": {
        "MySql": {
          "DisableHealthChecks": true,
          "DisableTracing": true
        }
      }
    }
  }
}

Use inline delegates

You can also pass the Action<PomeloEntityFrameworkCoreMySqlSettings> configureSettings delegate to set up some or all the options inline, for example to disable health checks from code:

builder.AddMySqlDbContext<MyDbContext>(
    "mysqldb1",
    static settings => settings.DisableHealthChecks  = true);

or

builder.EnrichMySqlDbContext<MyDbContext>(
    static settings => settings.DisableHealthChecks  = true);

Health checks

By default, .NET Aspire components enable health checks for all services. For more information, see .NET Aspire components overview.

The The .NET Aspire Pomelo MySQL Entity Framework Core component registers a basic health check that checks the database connection given a TContext. The health check is enabled by default and can be disabled using the DisableHealthChecks property in the configuration.

Observability and telemetry

.NET Aspire components automatically set up Logging, Tracing, and Metrics configurations, which are sometimes known as the pillars of observability. For more information about component observability and telemetry, see .NET Aspire components overview. Depending on the backing service, some components may only support some of these features. For example, some components support logging and tracing, but not metrics. Telemetry features can also be disabled using the techniques presented in the Configuration section.

Logging

The The .NET Aspire Pomelo MySQL Entity Framework Core component uses the following log categories:

  • Microsoft.EntityFrameworkCore.Database.Command.CommandCreated
  • Microsoft.EntityFrameworkCore.Database.Command.CommandExecuting
  • Microsoft.EntityFrameworkCore.Database.Command.CommandExecuted
  • Microsoft.EntityFrameworkCore.Database.Command.CommandError

Tracing

The The .NET Aspire Pomelo MySQL Entity Framework Core component will emit the following tracing activities using OpenTelemetry:

  • OpenTelemetry.Instrumentation.EntityFrameworkCore

Metrics

The The .NET Aspire Pomelo MySQL Entity Framework Core component currently supports the following metrics:

  • Microsoft.EntityFrameworkCore

See also