Fix prevent zombie explorer.exe processes when opening folders

Flow.Launcher/PublicAPIInstance.cs

@@ -46,7 +46,7 @@
 
         // Must use getter to avoid circular dependency
         private Updater _updater;
         private Updater Updater => _updater ??= Ioc.Default.GetRequiredService<Updater>();
 
         private readonly object _saveSettingsLock = new();
 
@@ -142,7 +142,7 @@
             ShellCommand.Execute(startInfo);
         }
 
         [System.Diagnostics.CodeAnalysis.SuppressMessage("Usage", "VSTHRD100:Avoid async void methods", Justification = "<Pending>")]
         public async void CopyToClipboard(string stringToCopy, bool directCopy = false, bool showDefaultNotification = true)
         {
             if (string.IsNullOrEmpty(stringToCopy))
@@ -316,22 +316,46 @@
 
         public void OpenDirectory(string DirectoryPath, string FileNameOrFilePath = null)
         {
-            using var explorer = new Process();
+            string targetPath;
+
+            if (FileNameOrFilePath is null)
+            {
+                targetPath = DirectoryPath;
+            }
+            else
+            {
+                targetPath = Path.IsPathRooted(FileNameOrFilePath)
+                    ? FileNameOrFilePath
+                    : Path.Combine(DirectoryPath, FileNameOrFilePath);
+            }
+
             var explorerInfo = _settings.CustomExplorer;
+            var explorerPath = explorerInfo.Path.Trim().ToLowerInvariant();
+
+            // If explorer.exe, ignore and pass only the path to Shell
+            if (Path.GetFileNameWithoutExtension(explorerPath) == "explorer")
+            {
+                Process.Start(new ProcessStartInfo
+                {
+                    FileName = targetPath,         // Not explorer, Only path.
+                    UseShellExecute = true         // Must be true to open folder
+                });
+                return;
+            }
 
-            explorer.StartInfo = new ProcessStartInfo
+            // Custom File Manager
+            var psi = new ProcessStartInfo
             {
                 FileName = explorerInfo.Path.Replace("%d", DirectoryPath),
                 UseShellExecute = true,
                 Arguments = FileNameOrFilePath is null
                     ? explorerInfo.DirectoryArgument.Replace("%d", DirectoryPath)
                     : explorerInfo.FileArgument
                         .Replace("%d", DirectoryPath)
-                        .Replace("%f",
-                            Path.IsPathRooted(FileNameOrFilePath) ? FileNameOrFilePath : Path.Combine(DirectoryPath, FileNameOrFilePath)
-                        )
+                        .Replace("%f", targetPath)
             };
-            explorer.Start();
+
+            Process.Start(psi);
         }
 
         private void OpenUri(Uri uri, bool? inPrivate = null)