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With networking disabled, System.Net.Dns.BeginGetHostAddress() throws a SocketException with the error "no host found". This exception is unhandled and thrown in a background thread, causing the application to crash with no hope of catching the exception since it's in a thread beyond the developer's control.
1) Take the attached example and compile it in MonoDevelop on Linux
2) Run the application with access to the internet (networking is enabled)
expect: no issues, application completes normally
actual: as expected
3) turn off networking (for me, on Ubuntu 12, I unselected "Enable Wireless" from the wifi menu.
4) Run the app again
expected: no issues, application fails to look up the DNS entry for the provided name but does not crash
actual: crashes with an unhandled SocketException.
OS: Ubuntu 12.04.2 LTS "Precise", 32 bit
Mono: Mono JIT compiler version 18.104.22.168 (Debian 22.214.171.124-1ubuntu2.2)
Hardware: 7 year old MacBook with an Intel processor
Created attachment 3979 [details]
Small repro of the issue
This is Linux specific. At the very least, this does not happen on OSX Mountain Lion with Mono 2.10.12
Closing ancient bugs, please reopen if you're still having this problem.