如何在xmarine android c#应用程序中显示来自内部存储自定义文件夹的pdf？

我想在我的应用程序中下载（从内部存储自定义文件夹）后显示pdf文件。我希望用户可以选择自己喜欢的应用程序来打开它。我使用了下面提到的代码，但它不起作用。我该怎么做？

问题由

try
                    {
                        string extension = MimeTypeMap.GetFileExtensionFromUrl(Android.Net.Uri.FromFile(file).ToString());
                        string mimeType = MimeTypeMap.Singleton.GetMimeTypeFromExtension(extension);
                        Intent intent = new Intent(Intent.ActionView);
                        intent.SetFlags(ActivityFlags.ClearTop | ActivityFlags.NewTask);
                        Android.Net.Uri path = FileProvider.GetUriForFile(Application.Context, Android.App.Application.Context.PackageName + ".provider", file);
                        intent.SetDataAndType(path, mimeType);
                        intent.AddFlags(ActivityFlags.GrantReadUriPermission);
                        Application.Context.StartActivity(Intent.CreateChooser(intent, "Choose App"));
                    }
                    catch (Exception ex)
                    {
                        Toast.MakeText(Application.Context, "problem", ToastLength.Long).Show();
                    }

try
                    {
                        string extension = MimeTypeMap.GetFileExtensionFromUrl(Android.Net.Uri.FromFile(file).ToString());
                        string mimeType = MimeTypeMap.Singleton.GetMimeTypeFromExtension(extension);
                        Intent intent = new Intent(Intent.ActionView);
                        intent.SetFlags(ActivityFlags.ClearTop | ActivityFlags.NewTask);
                        Android.Net.Uri path = FileProvider.GetUriForFile(Application.Context, Android.App.Application.Context.PackageName + ".provider", file);
                        intent.SetDataAndType(path, mimeType);
                        intent.AddFlags(ActivityFlags.GrantReadUriPermission);
                        Application.Context.StartActivity(Intent.CreateChooser(intent, "Choose App"));
                    }
                    catch (Exception ex)
                    {
                        Toast.MakeText(Application.Context, "problem", ToastLength.Long).Show();
                    }