Missing DLLImport even though there is a "using InteropServices"

Question

I have the following code:

using System; using System.Collections.Generic; using System.Linq; using System.Runtime.InteropServices; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; using MapsApp.DB;  namespace MapsApp {     public partial class _Default : System.Web.UI.Page     {         [DLLImport("GeoUrbanApp.exe")]         public static extern double CalcFigure(double east, double north, double size); ... 

I am trying to call the CalcFigure function from the .exe. I've added it in the references, and trying to import it. All I get is:

The type or namespace name 'DLLImport' could not be found (are you missing a using directive or an assembly reference?)  The type or namespace name 'DLLImportAttribute' could not be found (are you missing a using directive or an assembly reference?) 

The solution most people find online is the "using System.Runtime.InteropServices;" but I have it.

Answer 1

Try adding

using System.Runtime.InteropServices;

to your class, that's the namespace the DllImportAttribute resides in.

Answer 2

It's DllImport not DLLImport

:)