Add .NET 4.5 specific project to support Task Based Async calls

[bkaid]

Added a QueryAsync method using .NET 4.5 style task based async call to ExecuteReaderAsync. Updated .nuspec file to include a .NET 4.5 library. Currently SQL server specific because SqlCommand defines ExecuteReaderAsync (not IDbCommand).

[mgravell]

Actually, this is defined on the DbCommand: http://msdn.microsoft.com/en-us/library/hh223695.aspx - if possible, the least-specific version is preferable; however, I think this is more complex than first appears. In particular, I've got consideration towards things that decorate the command pattern (mini-profiler etc). We might need to invest a bit of time thinking about how we do this correctly in the more general context. I imagine a task with continuation would do it.

I think jumping on the sql-server one would be a bit of a mistake, long-term. Might be better to hold on this for now, pending more investigation.

I am perfectly open to a new 4.5-specific build; that doesn't bother me.

[bkaid]

Thanks Marc - didn't catch that it was available on DbCommand. I updated my fork to use DbCommand instead of SqlCommand.

This attempt was as good as I could do. You and Sam are the experts here so I'll let you guys figure out the best approach. But it would be great if Dapper had built-in support for async querying.

[brannon]

+1 for Async support.

[antonheryanto]

👍 Async support too

[mgravell]

I've merged this; thanks! Note: was a manual merge (conflicts etc), but seems to work. My preference would be to drag this into the core dll for 4.5, rather than a second nuget package - any thoughts on that? Have a look at the merged base and let me know.

[bkaid]

Thanks Marc. I agree it would be great to have in the core nuget package and once its available I'll update the notes on my dapper-async nuget to indicate that the package is deprecated since the functionality has been moved to core dapper package.