I was developing a webpart in sharepoint ( consider it as a asp.net usercontrol for ASP.Net Developers) and in the webpart i was uploading a document using AsyncFileUpload control in AJAX Toolkit.
And it was working fine, but for some files i was getting this error : "Cannot open a closed file" and i was thinking that the problem from the file or it is a code behind issue.
I figure out the problem was because of the file size threshold in the web.config, the default web.config is:
<httpruntime maxrequestlength="51200" />
I added this attribute:
<httpruntime maxrequestlength="51200" requestLengthDiskThreshold="4096" />
The resolution for the problem is: Set the length disk threshold to 4M ( or any other number in KB as per your application business rule) because by default the value is 80K.
Hope this helps.
Happy SharePointing.... or .Netting :)