空捕获，但仍引发异常

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.

Answer 1

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.