'function' : cannot explicitly call operator or accessor
Certain operators have internal names. For example, op_Increment is the internal name of the ++ operator. You should not use or explicitly call such method names.
The following sample generates CS0571:
public class MyClass { public static MyClass operator ++ (MyClass c) { return null; } public static int prop { get { return 1; } set { } } public static void Main() { op_Increment(null); // CS0571 // use the increment operator as follows // MyClass x = new MyClass(); // x++; set_prop(1); // CS0571 // try the following line instead // prop = 1; } }