float.Parse() doesn't work the way I wanted

I have a text file,which I use to input information into my application.The problem is that some values are float and sometimes they are null,which is why I get an exception.

        var s = "0.0";
        var f = float.Parse(s);

The code above throws an exception at line 2 "Input string was not in a correct format."

I believe the solution would be the advanced overloads of float.Parse,which include IFormatProvider as a parameter,but I don't know anything about it yet.

How do I parse "0.0"?