Intro
C# is a C++ derived language using elements of several others, while avoiding the pitfalls of these languages. C# works with the Microsoft .NET framework. C# was designed to be a simple, modern approach to making coding possible for the everyday person while being powerful enough to create large applications.
Sample Program
using System;
namespace HelloWorld
{
class Class1
{
static void Main(string[] args)
{
Console.WriteLine("Hello, world!");
}
}
}
ASP.NET (Active Server Pages .NET)
ASP.NET is a technology for the development of web pages / applications in any .NET language.
The Mono Project
The Mono project provides the necessary software to develop and run .NET applications on the Mac and Linux platforms. Sponsored by Novell, Mono is fully Open-Source and also supports ASP.NET.
You can check out Mono here.
Useful Links
SDKs and IDEs (Software Development Kits and Integrated Development Environments)
C# is most easily developed using Microsoft's SDK, Visual C# 2008, since C# is a namely Microsoft creation.
For ASP.NET, there is Microsoft's Visual Web Developer Express. You can get that here.
Help Files
There are many pages about C#. The easiest way is to search Google.
Related Languages
Since C# is very similar to C and C++, you should take a look at those pages too.