Consider adding FillAsync and async APIs on data adapters #22109

Core 2.0 preview 1 now supports SqlDataAdapter and DataTable which is great and the best way to fill a DataSet from a stored procedure is by using SqlDataAdapter.Fill(DataSet). This works perfectly when not used in an async environment. There is currently no way in Core or full .NET to do a FillAsync. Without a FillAsync which would take a single line of code now requires 20 lines of much more complicated code including using SqlDataReader.GetSchemaTable() which is currently broken preview 1. Based on other posts I believe it will be working in Preview 2 but have not seen a definitive on that.

This is not something for 2.0 but is a clear deficiency in truly being able to support a fully async back-end and would be a much needed improvement moving forward.