SQL Server: You can prefix any query with
SET DATEFORMAT MDY;
SQL Server accepts MDY, DMY, YMD (and even YDM though why I dunno).
Note that you only need to do this once per open connection, so if you execute multiple queries on the same connection, you only need this once. But it won't hurt to do it with each query. You can also change the installation default, but I dunno if you can change the default on a per-user basis.
, no ASP.NET code needed/wanted.