CODEWITHSUNDEEP
c++-clipinvoke
Артём Царионов
Артём Царионов

Reputation: 1037

Unable to find an entry point

I import two WinApi functions and use them in my class

using namespace System::Runtime::InteropServices;

[DllImport("user32",ExactSpelling = true)]
extern bool CloseWindow(int hwnd);
[DllImport("user32",ExactSpelling = true)]
extern int FindWindow(String^ classname,String^ windowname);

public ref class WinApiInvoke
{
public:
    bool CloseWindowCall(String^ title)
    {
        int pointer = FindWindow(nullptr,title);
        return CloseWindow(pointer);
    }
};

Then I create object in main program and call CloseWindowCall method

Console::WriteLine("Window's title");
String ^s = Console::ReadLine();
WinApiInvoke^ obj = gcnew WinApiInvoke();
if (obj->CloseWindowCall(s))
    Console::WriteLine("Window successfully closed!");
else Console::WriteLine("Some error occured!");

When I write in console for example Chess Titans to close I've got an error Unable to find an entry point named 'FindWindow' in DLL 'user32'

What entry point?

Upvotes: 0

Views: 1463

Answers (1)

Hans Passant
Hans Passant

Reputation: 941585

You are using the ExactSpelling property inappropriately. There is no FindWindow function in user32.dll, just like the exception message says. There is FindWindowA and FindWindowW. The first one handles legacy 8-bit character strings, the second uses Unicode strings. Any Windows api function that accepts strings has two versions, you don't see this in C or C++ code because the UNICODE macro selects between the two.

Avoid ExactSpelling on winapi functions, the pinvoke marshaller knows how to deal with this. You have some other mistakes, the proper declaration is:

[DllImport("user32.dll", CharSet = CharSet::Auto, SetLastError = true)]
static IntPtr FindWindow(String^ classname, String^ windowname);

Upvotes: 2

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