adding c style dll to c# app

[saleh]

hi,

i have a dll with its .h file,in the .h i found the [ extern "C" ] .
when i tried to add the dll to a c# app ,it give me that error
[please make sure that it is a valid com or assembly component]

so does anyone could help me to add the .dll to my app.

note: i don't have the source code.

thanks.