SimpleLink is a very simple .NET/Link example program demonstrating various methods from the IKernelLink interface. Look at the .NET/Link API Documentation for more information on .NET/Link programming.
The source is provided in C# and Visual Basic .NET versions, and there is also a compiled program, SimpleLink.exe.
You will notice that a copy of the .NET/Link assembly, Wolfram.NETLink.dll, is located in the same directory as SimpleLink.exe. This is how .NET/Link applications will always be deployed (Wolfram.NETLink.dll is not a strong-named assembly and therefore cannot be placed into the Global Assembly Cache).
You can use Visual Studio .NET to compile this program, but here is how to do it using the command-line C# and VB.NET compilers, which are included free with the .NET Framework SDK (and with Visual Studio .NET of course). First, make sure that the compilers (csc.exe or vbc.exe) are on your PATH. If you have Visual Studio .NET installed, the easiest thing to do is use the "Visual Studio .NET Command Prompt" choice in the Microsoft Visual Studio .NET/Visual Studio .NET Tools program group on the Start menu. This will open up a command window with all the required environment variables set correctly.
From the comand line:
csc /target:exe /reference:Wolfram.NETLink.dll SimpleLink.cs
From the comand line:
vbc /target:exe /reference:Wolfram.NETLink.dll SimpleLink.vb