How to match selected files from the folder browser to hide rows from the grid-view which is already saved in db?

      // Imagine that we have only stored the names of a.txt, b.csv and c.png
      // Further; pretend that from here...
      List<string> storedFileList = new List<string>();
      storedFileList.AddRange(new string[] {"a.txt", "b.csv", "c.png"});

      DataTable storedFiles = new DataTable();
      storedFiles.Columns.Add(new DataColumn("filename", typeof(string)));
      foreach (string name in storedFileList)
      {
        storedFiles.LoadDataRow(new object[] {name}, true);
      }
      // ...to here is the DB query that retrieves the previously stored filenames and 
      // dumps them into a datatable (or dataview).

      var qryAlreadyStored = from DataRow r in storedFiles.Rows
                             select r["filename"];

      // Now just filter out the files that we've already seen listing them
      // in ascending alphabetical order.
      string path = @"C:\TheDirectory\PathThat\WeAre\InterestedIn";
      DirectoryInfo dir = new DirectoryInfo(path); 
      var qryFile = from FileInfo file in dir.GetFiles()
                    where !qryAlreadyStored.ToList().Contains(file.Name)
                    orderby file.Name ascending
                    select file.Name; 
      
      // Reuse the same table structure for our grid.
      DataTable filesToDisplay = storedFiles.Clone();
      foreach (string newName in qryFile) 
      {
        filesToDisplay.LoadDataRow(new object[] {newName}, true);
      }

      TheGrid.DataSource = filesToDisplay;
      TheGrid.DataBind();

</string></string>