Empty catch but exception is still thrown

Question

Have a look at the following source code

 private IEnumerable<string> GetAntivirusSoftwareFromNamespace(string @namespace) { try { var wmipathstr = string.Format(@"\\{0}{1}", Environment.MachineName, @namespace); var searcher = new ManagementObjectSearcher(wmipathstr, "SELECT * FROM AntivirusProduct"); return from ManagementObject managementObject in searcher.Get() select managementObject.Properties["displayName"].Value.ToString(); } catch { // ignored } return Enumerable.Empty<string>(); }

And I call it with the following piece of code

 antivirusSoftware.AddRange(GetAntivirusSoftwareFromNamespace(@"\root\SecurityCenter")); antivirusSoftware.AddRange(GetAntivirusSoftwareFromNamespace(@"\root\SecurityCenter2"));

As you can see, the expcetion is ignored - which works fine on my computer. However if I run it on my staging server (which is Windows Server 2016 Standard) the exception is still thrown. Here's the stack trace

Unbehandelte Ausnahme: System.Management.ManagementException: Ungültige Klasse bei System.Management.ManagementException.ThrowWithExtendedInfo(ManagementStatus errorCode) bei System.Management.ManagementObjectCollection.ManagementObjectEnumerator.MoveNext() bei System.Linq.Enumerable.d__94`1.MoveNext() bei System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
bei System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection) bei protocol.client.Service.Modules.Information.InformationService.GetAntivirusSoftware() in C:\TeamCity\buildAgent\work\a41c7d46cc4907de\src\client\Service\Modules\Information\InformationService.cs:Zeile 70.

Any idea what could be the cause on this or how to fix it? I don't have visual studio or a debugger installed on the staging server.

Jon Skeet · Accepted Answer · 2017-01-22 17:48:29Z

The exception isn't thrown within the method you've shown - you're basically returning a query to the caller, and that query is then failing.

One option would be to force the query to execute immediately by calling ToList(). That way, any exceptions would be thrown within the method itself, so you could catch them:

return searcher.Get() .Select(mo => mo.Properties["displayName"].Value.ToString()) .ToList();

Having said that, I'd strongly advise against having such an empty, blanket catch block - that basically says, "I don't care what's gone wrong, I want my code to keep running regardless, and I don't even want to log what the problem is." If you want to guard against ManagementException, catch that specific exception instead - and consider logging it so you can try to avoid it in future.

Ah damnit, you're totally right. The LINQ query is executed in return within the AddRange method... How could I be that stupid - obvious things are the worst.. Thanks alot! And yeah, I'm gonna catch the ManagementException now, thanks for your advise!

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