First, we need to know what. sdf is? The sdf File is a localized Database File in Visual Studio 2010: SQL Server Compact Edition Database File. It has been verified that this file is saved as a database file by project information. If you have not participated in a large team project and do not involve a deep debugging process, this file is useless to you, you can safely delete the file. If you need it again later, it's easy to open the file in the project. the link for re-compiling the sln file is OK.
Official notes:
File Type 1: SQL Server Compact Database File
File description:
Compact relational database developed by Microsoft, also known the SQL Server Compact (SQL CE) format; designed for applications that run on mobile devices and have tops; contains the complete database contents and can be up to 4 GB in size.
NOTE:
Previous versions of SQL Server Compact were distributed as SQL Server for Windows CE and SQL Server Mobile Edition.
Note:
The file format can be opened under vs2010 and vs2012. Vs2013 cannot be opened.
To enable it, install:
Microsoft SQL Server Compact
Flyhoward SDF Viewer
Browsing in vs2013 requires: CompactView or l SQL Server Compact Toolbox extension
Or install SQL management Studio 2008.
If you do not need this file, simply delete it.