IDbCommand missing ExecuteReaderAsync

Question

I'm using .NET Core 2.0. I've got the following function that calls IDbCommand.ExecuteReader

public async Task<IEnumerable<Widget>> ReadAllAsync(
    System.Data.IDbConnection databaseConnection,
    System.Data.IDbTransaction databaseTransaction)
{
    var commandText = "SELECT WidgetId, Name FROM Widget";

    // _databaseCommandFactory.Create returns an IDbCommand
    var command = this._databaseCommandFactory.Create(databaseConnection, databaseTransaction, commandText);

    using (var dataReader = command.ExecuteReader())
    {
        // iterate through the data reader converting a collection of Widgets (`IEnumerable<Widget>`)
    }
}

I get a warning

This async method lacks 'await' operators and will run synchronously. Consider using the 'await' operator to await non-blocking API calls, or 'await Task.Run(...)' to do CPU-bound work on a background thread.

I was thinking about converting the command.ExecuteReader() statement to await Task.Run(() => command.ExecuteReader()) as advised in the warning. But I'm not sure this is the correct approach, I believe Task.Run(...) is for doing CPU based work. This is primarily IO work.

So my questions are

1. Is Task.Run(...) the correct approach?
2. If not, is there another solution?
3. Or should I just ignore the warning for now and wait until ExecuteReaderAsync gets added to the IDbCommand interface? (is there a plan for this?)

Answer 1

The await keyword is what allows the method to run asynchronously. The async keyword enables the use of the await keyword within the method and assists in managing the return.

Until await is called the method will run synchronously.

So all of this runs synchronously. It will not return anything or move through the method until it has completed.

public async Task<IEnumerable<Widget>> ReadAllAsync(
    System.Data.IDbConnection databaseConnection,
    System.Data.IDbTransaction databaseTransaction)
{
    var commandText = "SELECT WidgetId, Name FROM Widget";

    // _databaseCommandFactory.Create returns an IDbCommand
    var command = this._databaseCommandFactory.Create(databaseConnection, databaseTransaction, commandText);

    using (var dataReader = command.ExecuteReader())
    {
        // iterate through the data reader converting a collection of Widgets (`IEnumerable<Widget>`)
    }
}

By casting to DbCommand, which most IDbCommand derived implementations already do, then casting to DbCommand and adding await would work e.g.

var dbCommand = (DbCommand) command;
using (var dataReader = await dbCommand.ExecuteReaderAsync())
{
    while (await dataReader.ReadAsync()) 
    {
        // iterate through the data reader converting a collection of Widgets (`IEnumerable<Widget>`)
    }
}

or creating a separate Task

public async Task MyAsyncMethod()
{
  // Do your stuff that takes a long time
}

public async Task CallMyAsyncMethod()
{
  // We can await Tasks, regardless of where they come from.
  await MyAsyncMethod();

}

This way - the program will continue while awaiting the return from this method, rather than locking up the UI and all else.