You may have multiple files in one project. Before you ship the application to customer/end user, you must compile them into binary executable. You will not give the source files to the end user. Only the binary executable is required to run the application.
The process of compiling source files into binary executable is called "Build"
VWD and VS.NET comes with a handy feature to compile and organize all source files. This process is usually referred to as "build" process.
Before you can run a web site or windows application, you must build the project - which means that you must compile all files of the project.
Compiling files from command line is a pain. You have to pass several parameters to the compiler command. You must specify the source file to compile, the name of the binary executable to be generated etc.
How to build a web site using VWD ?
When you use VWD or Visual Studio to build an application - it is just one button click. There are couple of ways you can do this in VWD:
1. Click on the shortcut toolbar for Build
2. Use the menu option
Build -> Build Solution
3. Use the keyboard shortcut
Ctrl + Shift + B
When you use any of the above options to build a solution, Visual Studio does the following:
1. Identifies all the files part of the project.
2. Checks for compilation errors for each file in the solution.
Older versions of ASP.NET projects used to compile all the source files into an assembly and put them into a folder called "Bin". From ASP.NET 2.0 onwards, there won't be any "bin" folder created. Instead, source files will be compiled dynamically when a request is made for that particular piece of code. However, when you "build" the solution using Visual Studio, it verifies each file for compilation errors to avoid any compilation error during run time.
In case of windows application, all files are compiled into an executable.