To enable large file uploads you need to change the value of the following attributes on the system.web/httpRuntime configuration element:
maxRequestLength: Specifies the limit for the input stream buffering threshold in KB and allows you to control the allowed total size of the upload. Anything bigger than that will result in the default for the framework "Page not found" error.
ExecutionTimeout: Specifies the maximum number of seconds for which a request is allowed to be executed before being automatically shut down by ASP.NET – the default time is 110 seconds. If the request takes longer to be executed, an exception will be thrown.
maxAllowedContentLength (IIS 7) - specifies the maximum length of content in a request supported by IIS. By default it restricts the content length to 30,000,000 bytes.
Refer this link:
http://blogs.telerik.com/aspnet-ajax/posts/13-07-15/upload-large-files-asp-net-radasyncupload[
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