CKEDITOR.instances["page_content"].on("instanceReady", function() 
    { 
            //set keyup event 
            this.document.on("keyup", updateTextArea); 
             //and paste event 
            this.document.on("paste", updateTextArea); 
 
    }); 
 
    function updateTextArea() 
    { 
        CKEDITOR.tools.setTimeout( function() 
              {  
                $("#page_content").val(CKEDITOR.instances.page_content.getData()); 
                $("#page_content").trigger('keyup'); 
              }, 0);  
    } 

<script language="javascript" type="text/javascript">   
 
  function checkForm() 
       { 
         var f=document.form1; 
         var topicHeading=f.tbTopicHeading.value; 
         topicHeading = topicHeading.replace(/^\s+/g,""); 
         topicHeading = topicHeading.replace(/\s+$/g,""); 
                 if (topicHeading =="") 
                  { 
                    alert("请输入发表话题的标题."); 
                    f.tbTopicHeading.focus(); 
                    return false; 
                  } 
                  if(topicHeading.length>50); 
                  { 
                   alert("话题的主题长度必须在50字符以内."); 
                   f.tbTopicHeading.focus(); 
                   return false; 
                  } 
         var topicContent=CKEDITOR.instances.mckeditor.getData(); 
          
         topicContent = topicContent.replace(/^\s+/g,""); 
         topicContent = topicContent.replace(/\s+$/g,""); 
                 if (topicContent =="") 
                  { 
                    alert("请填写话题内容."); 
                    f.mckeditor.focus(); 
                    return false; 
                  }  
 
                  if(topicContent.length>4000) 
                  { 
                   alert("话题内容的长度必须在4000字符以内."); 
                   f.mckeditor.focus(); 
                   return false; 
                  }       
 
       }  
       </script> 

function InitRules() { 
      opts = { 
         rules: 
         { 
            tbTopicHeading:{ 
            required:true, 
            maxlength:50   
          },           
          mckeditor:{ 
            required:true, 
            maxlength:4000 
          }  
         }, 
         messages: 
         { 
          tbTopicHeading:{ 
          required:"请输入发表话题的标题.", 
          maxlength:jQuery.format("话题的主题长度必须在50字符以内.")  
        }, 
          mckeditor:{ 
          required:"请填写话题内容.", 
          maxlength:jQuery.format("话题内容的长度必须在4000字符以内.")  
        } 
         }  
      } 
    } 

<script type="text/javascript"> 
//<![CDATA[ 
CKEDITOR.instances["mckeditor"].on("instanceReady", function()    
    {    
            //set keyup event  
            this.document.on("keyup", updateTextArea);  
             //and paste event 
            this.document.on("paste", updateTextArea);   
    });    
 
    function updateTextArea()  
    {    
        CKEDITOR.tools.setTimeout( function() 
              {    
                $("#mckeditor").val(CKEDITOR.instances.mckeditor.getData());    
                $("#mckeditor").trigger('keyup');    
              }, 0);  
    }   
//]]> 
              </script> 

<asp:TextBox ID="mckeditor" runat="server" TextMode="MultiLine" Width="98%" Height="400px" CssClass="ckeditor"></asp:TextBox> 
<script type="text/javascript"> 
//<![CDATA[ 
CKEDITOR.replace( '<%=mckeditor.ClientID %>',// mckeditor.ClientID为TextBox mckeditor生成的对应客户端看到的id 
{ 
skin : 'kama',//设置皮肤 
enterMode : Number(2),//设置enter键的输入1.<p>2为<br/>3为<div> 
shiftEnterMode : Number(1), // 设置shiftenter的输入 
disableNativeSpellChecker:false,  
scayt_autoStartup:false, 
toolbar_Full : [ 
['Source','-','Save','NewPage','Preview','-'], 
['Cut','Copy','Paste','PasteText','PasteFromWord','-'], 
['Undo','Redo','-','Find','Replace','-','SelectAll','RemoveFormat'], 
['NumberedList','BulletedList','-','Outdent','Indent'], 
['JustifyLeft','JustifyCenter','JustifyRight','JustifyBlock'], 
['Link','Unlink','Anchor'], 
['Image','Table','HorizontalRule'],['Subscript','Superscript'], 
'/', 
['Bold','Italic','Underline'], 
['TextColor','BGColor'], 
['Styles','Format','Font','FontSize'] 
], 
//filebrowserBrowseUrl: '<%=ResolveUrl("~/ckfinder/ckfinder.html")%>', //启用浏览功能，正式使用场合可以关闭，只允许用户上传 
//filebrowserImageBrowseUrl:'<%=ResolveUrl("~/ckfinder/ckfinder.html?Type=Images")%>', 
//filebrowserImageUploadUrl:'<%=ResolveUrl("~/ckfinder/core/connector/aspx/connector.aspx?command=QuickUpload&type=Images")%>' 如果使用ckfinder 就不要屏蔽 
//自定义的上传 
filebrowserImageUploadUrl:'<%=ResolveUrl("~/fileupload/fileupload.aspx?command=QuickUpload&type=Images")%>' 
}); 
CKEDITOR.instances["mckeditor"].on("instanceReady", function()  
    { 
            //set keyup event 
            this.document.on("keyup", updateTextArea);  
             //and paste event 
            this.document.on("paste", updateTextArea);  
    });  
 
    function updateTextArea() 
    { 
        CKEDITOR.tools.setTimeout( function()  
              { 
                $("#mckeditor").val(CKEDITOR.instances.mckeditor.getData());  
                $("#mckeditor").trigger('keyup');  
              }, 0);  
    }   
//]]> 
              </script>