If the AJAX call to the server take too much time, then there is a possibility that user might press some other buttons or some other event occurred which will cause your AJAX call to stop and make a new request.
To overcome this situation, I decided to have div on the top of the page so that while AJAX call is in progress user cannot do any thing else.
So I simply Drag and Drop a Update Progress Control and write the following stuff.
<asp:UpdateProgress ID="UpdateProgress1" runat="server">
<ProgressTemplate>
<div id="Progress">Please wait ......</div>
<div id="bgDiv"></div>
</ProgressTemplate>
</asp:UpdateProgress>
And add the following style on head section of the page.
1: <style>
2: #bgDiv { 3: position:absolute;
4: top:0px;
5: bottom:0px;
6: left:0px;
7: right:0px;
8: overflow:hidden;
9: padding:0;
10: margin:0;
11: background-color:black;
12: filter:alpha(opacity=50);
13: opacity:0.5;
14: z-index:500;
15: }
16: #Progress
17: { 18: position: absolute;
19: background-color:Red;
20: width: 300px;
21: z-index: 600;
22: }
23:
24:
25: </style>
There we go whenever AJAX call made, a background div will appear and on top of that we have our message "Please wait"
Here is the snapshot
