C # when calling the so library of mingw, DLL ###. so cannot find the specified module,

C # when calling the so library of mingw, DLL ###. so cannot find the specified module,

When C # is used to call the so of mingw, it is reported that c # cannot load the DLL "###. so". The specified program cannot be found. (Exception from HRESULT: 0x8007007E)
I thought it was a dll path problem. I still cannot solve it after I confirm the full path is correct.
Then, by loading other so files, we found that the function symbol could not be found, rather than the specified program.
So I think it is the specific problem of this so, and check the number of digits of the so file, and the number of digits of the C # program, both are 32 bits.
After analysis, if the dll location can be determined to be correct, the called DLL file must be correctly referenced when used in other DLL files. Therefore, comments the libtiff part referenced by the so file and try again.
The possible cause is the compiler problem. Because the regular expression is used in c ++, the g ++ of mingw is upgraded from 4.8.2 to 6.3, so the compiler is successfully executed after being changed back to the original earlier version.
After successful execution, we found that the exe path contains the mingw runtime dll:
Libgcc_s_dw2-1.dll, libstdc ++-6.dll, libwinpthread-1.dll
Previously, in order to facilitate deployment and copy to the executable program path, and these files are in version 4.8.2, the 6.3 version is also working normally after being cleared.