Code-behind
In ASP.NET, code-behind files are that contain the actual programmatic logic. In ASP.NET, the logic and presentation are separated using code-behind files. The presentation is the .aspx or .ascx files.
In the traditional ASP style of development, the coding logic has to be nessecarily embedded into the HTML. This made writting code and maintaining it extremely difficult. All the code is written in a single .asp file.
In ASP.Net two files are created in place of the single .asp file.
- .aspx - This file contains the HTML, the Server-side controls and the Javascript. Thus it is pure data representation.
- .aspx.cs or .aspx.vb - This contains the actual logic for data control. This make debuging and maintainance easier. The file is suffixed by a .cs (C#) or .vb (Visual Basic) depending on the language used to program.
Hence a Code-Behind is exactly what it is, a code behind the actual HTML.