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AsyncPoco

2.0 is here! For details and help transitioning from 1.x, check out the upgrade guide.

AsyncPoco is a fork of the popular PetaPoco micro-ORM for .NET, with a fully asynchronous API and broad cross-platform support, including .NET Core. If you're familiar with PetaPoco and the TAP pattern (i.e. async/await), the transition to AsyncPoco should be quite intuitive.

var db = new AsyncPoco.Database("connectionStringName");

var count = await db.ExecuteScalarAsync<long>("SELECT Count(*) FROM articles");
var a = await db.SingleOrDefaultAsync<Article>("SELECT * FROM articles WHERE article_id = @0", 123);
var result = await db.PageAsync<Article>(1, 20, // <-- page number and items per page
        "SELECT * FROM articles WHERE category = @0 ORDER BY date_posted DESC", "coolstuff");

await db.ExecuteAsync("DELETE FROM articles WHERE draft<>0");
await db.DeleteAsync<Article>("WHERE article_id = @0", 123);
await db.UpdateAsync<Article>("SET title = @0 WHERE article_id = @1", "New Title", 123);
await db.SaveAsync(a);

One imporant note is that the constructor in the example above is not supported in .NET Core. In a config file, a connection string generally includes a providerName, which resolves to a globally registered ADO.NET provider. Unfortunately, this functionality is absent in .NET Core, so AsyncPoco requires that you pass the provider a bit more directly. This is still pretty painless; either of these will work:

var db = Database.Create<MySqlConnection>("connectionString");
var db = Database.Create(() => new OracleConnection("connectionString"));

One case where the transition to AsyncPoco might be less straightforward is the Query method. In PetaPoco, Query<T> (and its various overloads) returns IEnumerable<T>, and its implementation yield returns POCOs as it streams results from the underlying DataReader. But AsyncPoco's QueryAsync<T> methods do not return Task<IEnumerable<T>>. The reason is that if you await a method with that signature, you will not have results to work with until the Task completes, meaning all results are pulled into memory, at which point you may as well Fetch a List<T>. Ideally, you want to be able to process the results asynchronously as they become available. So instead of returning a result that can be enumerated, QueryAsync<T> accepts a callback that is invoked for each POCO in the result set as it becomes available.

await db.QueryAsync<Article>("SELECT * FROM articles", a =>
{
    Console.WriteLine("{0} - {1}", a.article_id, a.title);
});

What if you want to stop processing results before you reach the end of the DataReader's stream? There is a set of QueryAsync<T> overloads that take a Func<T, bool> callback; simply return false from the callback to hault the iteration immediately and close/dispose the DataReader.

await db.QueryAsync<Article>("SELECT * FROM articles", a =>
{
    if (IsWhatIWant(a))
    {
        Console.WriteLine("Found it! {0} - {1}", a.article_id, a.title);
        return false; // stop iterating and close/dispose the DataReader
    }
    else
    {
        return true; // continue iterating
    }
});

What databases are supported?

AsyncPoco supports the following database platforms:

What flavors of .NET are supported?

AsyncPoco targets full .NET Framework as well as .NET Standard 1.3 and 2.0, meaning it will run on the following platforms:

Is it faster than PetaPoco?

No. But that's not the point of asynchronous code. The point is to free up threads while waiting on I/O-bound work to complete, making desktop and mobile apps more responsive and web applications more scalable.

Why shouldn't I switch from PetaPoco?

Once you start converting synchronous code to async, it's said to spread like a zombie virus, meaning that if you're dealing with a large codebase, be prepared to make a substantial number of changes. If don't have the time or resources needed for this commitment, AsyncPoco is probably not a good fit. Going only partially async is an invitation for deadlocks. A good rule of thumb is if you've used .Wait() or .Result anywhere in your code (other than perhaps the Main method of a console app), you've done something wrong. You need to either use async all the way up and down your call stack, or not at all.

Where do I get it?

AsyncPoco is available via NuGet:

PM> Install-Package AsyncPoco

How do I get help?

How can I contribute?

I'll gladly accept pull requests that address issues and implement cool features, although I generally prefer that you create an issue first so we can discuss the specifics. I'd also be grateful for your help spreading the word via Twitter, blog posts, etc.

Credit where credit is due

Well over 90% of this code is the brainchild of Brad Robinson (@toptensoftware); I'm merely riding the coattails of PetaPoco's success. Brad in turn credits Rob Conery (@robconery) for original inspiration (ie: Massive), Rob Sullivan (@DataChomp) for hard core DBA advice, and Adam Schroder (@schotime) for lots of suggestions, improvements and Oracle support.