How to call a function in an unmanaged dll from C# Code?

How can I call the following method from C#, which is in a C++ dll? How Can I recreatethe following structure in C#?

C# calling unmanaged code

I am trying to call unmanaged code using C#. extern \"C\" __declspec(dllexport) LPBYTE DataReceived(LPBYTE signals)

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