aspnet_state_perf.h

C header file Reference

An .h file is a header file for the C and C++ programming languages. The file declares functions, types, and constants in plain text. Source files include the header with the include directive of the preprocessor. Libraries publish their programming interface in header files. Python packages with native extensions also ship .h files.

A file extension is only a part of the file name. It does not give a guarantee about the format or the content of a file. But on Windows, the extension selects the program that opens the file.