What does "candidate function(s) not accessible" mean?

I have a new managed C++ Form project (my first) and if I try to declare a StreamReader object I get an error that I don't understand:

Code:

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private: System::Void Form1_Load(System::Object^  sender, System::EventArgs^  e) {

                StreamReader sr;
}

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This generates an error on compiling:

error C3767: 'System::IO::StreamReader::StreamReader': candidate function(s) not accessible c:\my documents\visual studio 2008\projects\windowsforms\windowsforms\Form1.h

Can someone explain what this means please?
Thanks

You're trying to default-construct a StreamReader object. That class does have a default constructor, inherited from TextReader, but it's protected, so you can't access it from your code. That leads to the irritating error message you got instead of a plain "that doesn't exist". Use one of the several public StreamReader constructors instead.

Thank you very much. The MSDN explanation for this error is more cryptic than the error message.