Disable button after submit in Asp.net

<asp:Button  runat="server" ID="btnsubmit" Text="Submit"
OnClick="btnsubmit_Click" UseSubmitBehavior="false"
OnClientClick="this.disabled=true;this.value='Please wait..';"   />

For <asp:imagebutton> usesubmitbehavior will not work hence for this:

<asp:ImageButton runat=”server” ID=”btImageButton”
ImageUrl=”/images/submit.jpeg” OnClick=”btImageButton_Click”
OnClientClick=”javascript: Submit(this);” />

 <script type=”text/javascript” language=”javascript”>

function Submit(c){
Page_ClientValidate();
if (Page_IsValid){
c.disabled = true
__doPostBack(c.name, ”);
}
return Page_IsValid;
}

</script>