One software SDK affords some APIs by C++ class library, including the h, lib, dll files.
However, I want to use C# to work with the library.
So, are there any tools could package the C++ class library to C#? Or some suggestion?
I don’t want use CLI, because of so many classes.
Use C++/CLI, the dialect of C++ used in managed code on the .NET platform. The language was designed primarily for use in an application such as yours.
See this article (the title is a bit of an exaggeration, but the content is good). Other searches on wrappers for C++ code should give you more examples.
As Barry has pointed out, using a platform invoke (P/Invoke) call would let you call native code from a DLL.