Files with .CS extension are source code files for C# programming language. Introduced by Microsoft for use with the .NET Framework, the file format provides the low-level programming language for writing code that is compiled to generate the final output file in the form of EXE or a DLL. These can be created and compiled with Microsoft Visual Studio. Microsoft Visual Studio Express can also be used to create and update such files which is a free IDE. CS files are used for application development that can range from simple desktop applications to more complex programs. A simple Visual Studio project solution created with C# language can comprise of one or more such files. Files marked for inclusion in compilation are listed in the CSPROJ file which is part of the project and tells compiler to use the marked files.

CS File Format

CS files are text based file formats that can be opened in any text editor for editing. However, when opened in a supported IDE with proper syntax highlighting, the code is easy to read and arrange. A simple CS file contains:

  • Namespaces declaration - For referring to a particular functionality defined by that specific namespace
  • Variables declaration - To declare class level variables for the particular implementation
  • Methods Declaration - To declare methods declaration for the particular functionality

Syntax

  • Semicolons are used to denote the end of a statement.
  • Curly brackets are used to group statements. Statements are commonly grouped into methods (functions), methods into classes, and classes into namespaces.
  • Variables are assigned using an equals sign, but compared using two consecutive equals signs.
  • Square brackets are used with arrays, both to declare them and to get a value at a given index in one of them.

Example

using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("Hello, world!");
    }
}

How to open CS files?

Following applications can be used to open .CS files.

  • Microsoft Visual Studio
  • Microsoft Notepad
  • Notepad++
  • MonoDevelop