Best way of using MessageBox()?

Code:

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,LPSTR lpCmdLine, int nShowCmd)
{
	std::string line;
	
        //load a .txt file with a question in it
	std::ifstream myfile("question1q.txt");
	
         while(!myfile.eof())
	{
		getline(myfile,line);
		
	}
	myfile.close();

	MessageBox(NULL,/*I want to put the string named line right here*/,"The Question",MB_OKCANCEL);
	
	return 0;
}

I can't figure out a way to convert the string into something compatible with the second argument of MessageBox() I turned the project settings to using MultiByte and that helped a bit, but I'm still not quite getting this.
I'm just trying to make a simple program that asks a question and then shows you the answer. After I figure out how to make this part work, I'll be able to figure out the second.
the error that I usually get is
error C2664: 'MessageBoxA' : cannot convert parameter 2 from 'std::string' to 'LPCSTR' No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

I understand the gist of this message, but I'm was unable to find a way I understood to convert string to LPCSTR after scouring the web for about 15 minutes
Thanks, mjhamrick

p.s. if there is a better substitute for ifstream for windows programming, I'd love to hear it. This is just the only way I know to read from a text file as of now

MessageBoxA takes a LPCSTR (char *) as an argument...you can get one from a string through the std::string's .c_str() method.

But how do you use that method? I tried, and did something wrong because it made the program compile correctly but not run.
if I could just get the basic syntax for that method, I think I should be able to get it.

MessageBox(NULL,line.c_str(),"The Question",MB_OKCANCEL);
Btw, LPCSTR is const char*. LP = pointer, C = const, STR = char, so const char *.

Yep...brain fart on my part on the LPCSTR thing. Not really spending much time in the Windows C or C++ world at all lately.