如何检测待保存的文件？

问：

我正在尝试遵循谢尔盖对同一问题的评论，即如何检测具有“待处理保存状态”的文件。

法典：

using EnvDTE;
using EnvDTE80;
using Microsoft.VisualStudio.Shell;

namespace Link
{
    public static class ProjectHelpers
    {
        static ProjectHelpers()
        {
            // Rely on caller being on UI thread as shouldn't do it here in the constructor.
#pragma warning disable VSTHRD010 // Invoke single-threaded types on Main thread
            Dte = (DTE)Package.GetGlobalService(typeof(DTE));
#pragma warning restore VSTHRD010 // Invoke single-threaded types on Main thread
            Dte2 = (DTE2)Package.GetGlobalService(typeof(DTE));
        }

        public static DTE Dte { get; }

        public static DTE2 Dte2 { get; }
    }
}

然后我将 Dte.Documents 称为：

try
{
      await ThreadHelper.JoinableTaskFactory.SwitchToMainThreadAsync();

      // Enumerate through open documents
      foreach (Document doc in ProjectHelpers.Dte.Documents)
      {
         // Check if the document has unsaved changes
         if (!doc.Saved)
         {
            Console.WriteLine($"Unsaved changes in document: {doc.FullName}");
         }
      }
}
catch (Exception ex)
{
      Console.WriteLine(ex.Message);
}

但是我得到了这个例外：

The data necessary to complete this operation is not yet available. (Exception from HRESULT: 0x8000000A)

我错过了什么？