extern -- C# Keyword
- The extern modifier is used to declare a method that is implemented externally.
- A common use of the extern modifier is with the DllImport attribute when you are using Interop services to call into unmanaged code.
- In this case, the method must also be declared as static,
[DllImport("<dll Name>.dll")]
private static extern void <dll Method Name>();
private static extern void <dll Method Name>();