System.Net.WebException: The operation has timed out

I have modified below values in my Web.config, it has resolved my issue.

  <httpRuntime maxRequestLength="60000000" executionTimeout="60000000" />

 <requestFiltering>
       <requestLimits maxAllowedContentLength="60000000" />
     </requestFiltering>

Then you need to change applicationHost.config

open the %windir%\System32\inetsrv\config\applicationHost.config file

Change this:

From
<section name="requestFiltering" overrideModeDefault="Deny" />

To

<section name="requestFiltering" overrideModeDefault="Allow" />

If still you are facing error..try this..

HttpServerConnection objConn;
objConn.Timeout = 60000000;
ServicePointManager.MaxServicePointIdleTime = 60000000;

Ref:http://ajaxuploader.com/large-file-upload-iis-debug.htm