Error while checking if .txt file is open or not

[newbiee999]

I want to check if a file is open or not. If not then open it.

ifstream inputFile;
if (!inputFile.is_open())
{ inputFile.open("filename.txt"); }

When I try to run the code in Visual Studio 2013, I get an error that the "!" is illegal.

error C2276: '!' : illegal operation on bound member function expression 

But when I try to run the same exact code in Netbeans 8.0.2, it works perfectly.

Can someone help me with this?