在C＃中更改已修改的标头

Question

将网页浏览器控件中的网页保存到下面的代码目录中。现在我想检查每天修改或未修改的所有网页。如果它被修改必须更新或者保留它。

 long size = CalculateDirectorySize(dir, true);         
           mb = (size) / (1024 * 1024);            
        var filename1 = webBrowser1.Document.Title;

        var path1 = (@"D:\Cache\" + filename1 + ".html");
        if (mb != 1)
        {
            if (File.Exists(path1))
            {
                MessageBox.Show("Exist");
            }
            else
            {
                File.WriteAllText(path1, webBrowser1.Document.Body.Parent.OuterHtml, Encoding.GetEncoding(webBrowser1.Document.Encoding));
                MessageBox.Show("Saved");
            }
        }
        else
        {

          DialogResult dialogResult = MessageBox.Show("Cache Full!!  Want to Continue","Confirm", MessageBoxButtons.YesNo);
          if (dialogResult == DialogResult.Yes)
          {
              DirectoryInfo source = new DirectoryInfo("D:\\Cache");

              // Get info of each file into the directory
              foreach (FileInfo fi in source.GetFiles())
              {
                  var creationTime = fi.CreationTime;

                  if (creationTime < (DateTime.Now - new TimeSpan(7, 0, 0, 0)))
                  {
                      fi.Delete();
                      File.WriteAllText(path1, webBrowser1.Document.Body.Parent.OuterHtml, Encoding.GetEncoding(webBrowser1.Document.Encoding));
                  }



              }
              MessageBox.Show("Least Recently Used File Deleted And Saved New File");


          }
          else if (dialogResult == DialogResult.No)
          {
              MessageBox.Show("Thankyou","Alert");
          }

现在我想检查（自标题修改后）存储在D：\ Cache Daily中的所有网页。如果修改了必须更新并保存相同的文件夹。 请任何人解释我该怎么做并给出解决方案。