You can do some thing like this:

 

<script runat="server">
 
   string temp;
   void Page_Load(object sender, System.EventArgs e)
   {
      if (!IsPostBack)
      { 
        Editor1.Text={get your data source};        
        temp={get your data source};
      }  
 }

 public void Submit(object sender, System.EventArgs e)
 {
    if(temp==Editor1.Text)
    {
      //not changed
    }
    else
    {
      //changed
    }
 }
</script>

 

Hope it helps. Let me know if you have any further questions.