We have an application allowing the administrator to upload pdfs to the website.
In order to let the administrator uploads large files, we have set httpRuntime on web.config.
<httpRuntime executionTimeout="3600" maxRequestLength="1048576"
However, recently, we are getting the Invalid postback or callback argument error only when the file being upload is larger than 10MB. If the file is less than ~10MB, the system would upload fine.
If I set <%@ Page EnableEventValidation="fal
se" %>, there will be no error on the page, but the > 10MB pdf would not be uploaded either.
I have tested the application within the same network as the web server (to avoid longer time out issue); the same error appears.
Why does this problem only happen with larger file?
Thank you very much for your help
Invalid postback or callback argument. Event validation is enabled using <pages enableEventValidation="true"/> in configuration or <%@ Page EnableEventValidation="true" %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation.