Jul 15, 2015 · It will precompile each directory separately into <prefix>.<directoryName>.dll. Merge all pages and control outputs to a single assembly – This is the same as the -w option on aspnet_merge.exe. It will compile all of the UI pages (.aspx, .ascx, .master, etc…) into a single assembly.
By default, code files in a web application project are precompiled into a single assembly by using the Microsoft Build Engine (MSBuild). ASP.NET web pages (.aspx), user controls (.ascx), and MVC Razor views (.cshtml and.vbhtml) are compiled dynamically on the server by the ASP.NET compiler.