ScriptManager the EnablePageMethods attribute set javascript direct client services-called static WebMethod 

  EnablePageMethods.aspx 

  <script Type="text/javascript"> 
  Var txtName; 
  Var lblMsg; 
  Function pageLoad () ( 
  TxtName = new Sys.Preview.UI.TextBox ($ get ( 'txtName')); 
  LblMsg = new Sys.Preview.UI.Label ($ get ( 'lblMsg')); 
  ) 
  Function sayHello () ( 
  PageMethods.SayHello (txtName.get_text (), cb_SayHello); 
  ) 
  Function cb_SayHello (result) ( 
  LblMsg.set_text (result); 
  ) 
  </ Script> 

  <form Id="form1" runat="server"> 
<div>
  <asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="True"> 
<Scripts>
  <asp:ScriptReference Name="PreviewScript.js" Assembly="Microsoft.Web.Preview" /> 
  </ Scripts> 
  </ Asp: ScriptManager> 
  <input Type="text" id="txtName" /> 
  <input Type="button" value="invoke" onclick="sayHello()" /> 
  <div Id="lblMsg"> </ div> 
  </ Div> 
  </ Form> 

  EnablePageMethods.aspx.cs 

  [System.Web.Services.WebMethod] 
  Public static String SayHello (string name) 
  ( 
  Return "welcome to site" + name; 
  )