fix: handle unloaded projects using IVsHierarchy

Unloaded projects don't expose a Project object via the DTE automation
model. Use IVsMonitorSelection.GetCurrentSelection() to get the
IVsHierarchy and retrieve the project path via GetCanonicalName().

Author: CalvinAllen

src/CodingWithCalvin.OpenInNotepadPlusPlus/Helpers/ProjectHelpers.cs

@@ -1,8 +1,11 @@
 using System;
 using System.IO;
+using System.Runtime.InteropServices;
 using EnvDTE;
 using EnvDTE80;
+using Microsoft.VisualStudio;
 using Microsoft.VisualStudio.Shell;
+using Microsoft.VisualStudio.Shell.Interop;
 
 namespace CodingWithCalvin.OpenInNotepadPlusPlus.Helpers
 {
@@ -25,11 +28,62 @@ UIHierarchyItem selectedItem in (Array)
                         return GetProjectPath(project, dte.Solution);
                     case Solution solution:
                         return solution.FullName;
+                    default:
+                        // Handle unloaded projects - they don't expose a Project object
+                        // but we can get the path via IVsMonitorSelection and IVsHierarchy
+                        var path = GetPathFromHierarchy();
+                        if (!string.IsNullOrEmpty(path))
+                        {
+                            return path;
+                        }
+                        break;
                 }
             }
             return null;
         }
 
+        private static string GetPathFromHierarchy()
+        {
+            ThreadHelper.ThrowIfNotOnUIThread();
+
+            // Use IVsMonitorSelection to get the current selection's IVsHierarchy
+            // This works for unloaded projects where selectedItem.Object is not a Project
+            var monitorSelection = Package.GetGlobalService(typeof(SVsShellMonitorSelection)) as IVsMonitorSelection;
+            if (monitorSelection == null)
+            {
+                return null;
+            }
+
+            var hr = monitorSelection.GetCurrentSelection(out var hierarchyPtr, out var itemId, out _, out _);
+            if (hr != VSConstants.S_OK || hierarchyPtr == IntPtr.Zero)
+            {
+                return null;
+            }
+
+            try
+            {
+                var hierarchy = Marshal.GetObjectForIUnknown(hierarchyPtr) as IVsHierarchy;
+                if (hierarchy == null)
+                {
+                    return null;
+                }
+
+                // GetCanonicalName returns the full path for project files
+                if (hierarchy.GetCanonicalName(itemId, out var canonicalName) == VSConstants.S_OK
+                    && !string.IsNullOrEmpty(canonicalName)
+                    && File.Exists(canonicalName))
+                {
+                    return canonicalName;
+                }
+            }
+            finally
+            {
+                Marshal.Release(hierarchyPtr);
+            }
+
+            return null;
+        }
+
         private static string GetProjectPath(Project project, Solution solution)
         {
             ThreadHelper.ThrowIfNotOnUIThread();