The Microsoft .NET Framework Software Development Kit (SDK) is available for download from the Internet. The .NET Framework SDK is available as a free download at the .NET Framework Downloads site.
Downloading the .NET Framework SDK
The .NET Framework SDK includes the tools, code samples, and documentation that a developer might require to develop applications and business solutions that use the common language runtime (CLR).
Integration with SQL Server Compact 3.5 Books Online
After you have downloaded and installed the .NET Framework SDK, you can add it to SQL Server Compact 3.5 Books Online and SQL Server Management Studio, which will enable direct links from Books Online to the SDK documentation. For more information, see Help Collections (SQL Server Compact).