blocks|key|3055436|text|这可能是调试器的报告问题，而不是实际捕获异常。这篇文章给出了一些解决这个问题的技巧，如果是这样的话…Why+is+.NET+exception+not+caught+by+try/catch+block?|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3055437|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/36014/why-is-net-exception-not-caught-by-try-catch-block^0|1E|1G|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

This may be a reporting issue for the debugger, rather than not actually catching the exception. this post gives some tips on resolving it, if that is the case... <a href="https://stackoverflow.com/questions/36014/why-is-net-exception-not-caught-by-try-catch-block">Why is .NET exception not caught by try/catch block?</a>

blocks|key|3269105|text|What+is+a+First+Chance+Exception?|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3269106|3269107|+First+chance异常消息通常并不意味着代码中存在问题。对于优雅地处理异常的应用程序/组件，first+chance+exception消息让开发人员知道遇到了异常情况并得到了处理。|blockquote|3269108|3269109|entityMap|0|LINK|mutability|MUTABLE|url|http://blogs.msdn.com/davidklinems/archive/2005/07/12/438061.aspx^0|0|X|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|-4|5|6|7|U|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|V|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|W|8|@]|9|@]|C|$]]|$1|I|3|-4|5|6|7|X|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

<a href="http://blogs.msdn.com/davidklinems/archive/2005/07/12/438061.aspx" rel="nofollow noreferrer">What is a First Chance Exception?</a>

<blockquote>
 First chance exception messages most
 often do not mean there is a problem
 in the code. For applications /
 components which handle exceptions
 gracefully, first chance exception
 messages let the developer know that
 an exceptional situation was
 encountered and was handled.
</blockquote>

blocks|key|3269111|text|我能够复制你的问题，并产生了兴趣(因为我需要同样的东西)。我甚至研究了一种处理第一次机会异常的方法，但不幸的是，对于.net+Framework3.5及更低版本，这是不可能的(对于托管代码)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3269112|在我的例子中，每当服务出现问题或访问关闭的服务时，我总是得到一个System.ServiceModel.CommunicationObjectFaultedException。事实证明，c#的using语句是原因，因为在幕后，using语句总是关闭服务客户端实例，即使已经遇到异常(它不会直接跳到catch语句)。|offset|length|style|BOLD|CODE|3269113|每当using尝试关闭服务客户端实例时，原始异常System.ServiceModel.EndpointNotFoundException将被新的异常System.ServiceModel.CommunicationObjectFaultedException替换。|3269114|我提出的解决方案是不使用using语句，这样只要在try块中遇到异常，它就会立即向catch块抛出异常。|3269115|尝试编写类似这样的代码：|3269116|DashboardService.DashboardServiceClient+svc+=+new+Dashboard_WPF_Test.DashboardService.DashboardServiceClient();
try
{
++++svc.GetChart(0);
}
catch+(System.ServiceModel.EndpointNotFoundException+ex)
{
++++//handle+endpoint+not+found+exception+here
}
catch+(Exception+ex)
{
++++//general+exception+handler
}
finally
{
++++if+(!svc.State.Equals(System.ServiceModel.CommunicationState.Faulted)+&&+svc.State.Equals(System.ServiceModel.CommunicationState.Opened))
++++svc.Close();
}|code-block|syntax|javascript|3269117|而不是：|3269118|try
{
++++using+(DashboardService.DashboardServiceClient+svc+=+new+Dashboard_WPF_Test.DashboardService.DashboardServiceClient())
++++{
++++++++svc.GetChart(0);
++++}
}
catch+(System.ServiceModel.EndpointNotFoundException+ex)
{
++++//handle+endpoint+not+found+exception+here+(I+was+never+able+to+catch+this+type+of+exception+using+the+using+statement+block)
}
catch+(Exception+ex)
{
++++//general+exception+handler
}|3269119|然后你就能捕捉到正确的异常了。|3269120|entityMap^0|0|W|1J|2O|5|35|5|W|1J|2O|5|35|5|0|2|5|O|19|23|1J|2|5|O|19|23|1J|0|C|5|C|5|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|12|8|@$D|13|E|14|F|G]|$D|15|E|16|F|G]|$D|17|E|18|F|G]|$D|19|E|1A|F|H]|$D|1B|E|1C|F|H]|$D|1D|E|1E|F|H]]|9|@]|A|$]]|$1|I|3|J|5|6|7|1F|8|@$D|1G|E|1H|F|G]|$D|1I|E|1J|F|G]|$D|1K|E|1L|F|G]|$D|1M|E|1N|F|H]|$D|1O|E|1P|F|H]|$D|1Q|E|1R|F|H]]|9|@]|A|$]]|$1|K|3|L|5|6|7|1S|8|@$D|1T|E|1U|F|G]|$D|1V|E|1W|F|H]]|9|@]|A|$]]|$1|M|3|N|5|6|7|1X|8|@]|9|@]|A|$]]|$1|O|3|P|5|Q|7|1Y|8|@]|9|@]|A|$R|S]]|$1|T|3|U|5|6|7|1Z|8|@]|9|@]|A|$]]|$1|V|3|W|5|Q|7|20|8|@]|9|@]|A|$R|S]]|$1|X|3|Y|5|6|7|21|8|@]|9|@]|A|$]]|$1|Z|3|-4|5|6|7|22|8|@]|9|@]|A|$]]]|10|$]]

I was able to replicate your issue and got interested (since I needed the same). I even researched a way to handle \ catch first chance exceptions but unfortunately it is not possible (for managed code) for .net framework 3.5 and below.

On my case I always get a <code>System.ServiceModel.CommunicationObjectFaultedException</code> whenever something gets wrong on the service or whenever I access a down service. It turns out that c#'s <code>using</code> statement is the cause since behind the scene, the <code>using</code> statement always closes the service client instance even if an exception was already encountered (it doesn't jump to catch statement directly). 

What happens is that the original exception <code>System.ServiceModel.EndpointNotFoundException</code> will be replaced by the new exception <code>System.ServiceModel.CommunicationObjectFaultedException</code> whenever the <code>using</code> tries to close the service client instance.

The solution i've made is to not use the <code>using</code> statement so that whenever an exception is encountered inside the try block it will instantly throw the exception to the catch blocks.

Try to code something like:

<pre><code>DashboardService.DashboardServiceClient svc = new Dashboard_WPF_Test.DashboardService.DashboardServiceClient();
try
{
 svc.GetChart(0);
}
catch (System.ServiceModel.EndpointNotFoundException ex)
{
 //handle endpoint not found exception here
}
catch (Exception ex)
{
 //general exception handler
}
finally
{
 if (!svc.State.Equals(System.ServiceModel.CommunicationState.Faulted) &amp;&amp; svc.State.Equals(System.ServiceModel.CommunicationState.Opened))
 svc.Close();
}
</code></pre>

Instead of:

<pre><code>try
{
 using (DashboardService.DashboardServiceClient svc = new Dashboard_WPF_Test.DashboardService.DashboardServiceClient())
 {
 svc.GetChart(0);
 }
}
catch (System.ServiceModel.EndpointNotFoundException ex)
{
 //handle endpoint not found exception here (I was never able to catch this type of exception using the using statement block)
}
catch (Exception ex)
{
 //general exception handler
}
</code></pre>

And you'll be able to catch the right exception then.

blocks|key|316247|text|有关此可能的解决方案的详细信息，请查看。代码显示了generate+proxy的用法，但在ChannelFactory和其他平台上也是有效的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|316248|典型的here-be-dragons模式|316249|using+(WCFServiceClient+c+=+new+WCFServiceClient())
{
++++try
++++{
++++++++c.HelloWorld();
++++}
++++catch+(Exception+ex)
++++{
++++++++//+You+don't+know+it+yet+but+your+mellow+has+just+been+harshed.

++++++++//+If+you+handle+this+exception+and+fall+through+you+will+still+be+cheerfully+greeted+with+
++++++++//+an+unhandled+CommunicationObjectFaultedException+when+'using'+tries+to+.Close()+the+client.

++++++++//+If+you+throw+or+re-throw+from+here+you+will+never+see+that+exception,+it+is+gone+forever.+
++++++++//+buh+bye.
++++++++//+All+you+will+get+is+an+unhandled+CommunicationObjectFaultedException
++++}
}+//+<--+here+is+where+the+CommunicationObjectFaultedException+is+thrown|code-block|syntax|javascript|316250|正确的模式：|316251|using+(WCFServiceClient+client+=+new+WCFServiceClient())
{
++++try
++++{
++++++++client.ThrowException();

++++}
++++catch+(Exception+ex)
++++{
++++++++//+acknowledge+the+Faulted+state+and+allow+transition+to+Closed
++++++++client.Abort();

++++++++//+handle+the+exception+or+rethrow,+makes+no+nevermind+to+me,+my
++++++++//+yob+is+done+;-D
++++}
}+|316252|或者，正如您的问题中未使用using语句所表达的，|316253|WCFServiceClient+c+=+new+WCFServiceClient();

try
{
++++c.HelloWorld();
}
catch
{
++++//+acknowledge+the+Faulted+state+and+allow+transition+to+Closed
++++c.Abort();

++++//+handle+or+throw
++++throw;
}
finally
{
++++c.Close();
}|316254|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

Take a look at <a href="http://skysanders.net/subtext/archive/2010/04/19/the-proper-use-and-disposal-of-wcf-channels.-or-communicationobjectfaultedexception.aspx" rel="nofollow noreferrer">this post</a> for details on this possible solution. The code shows use of a generate proxy but is valid on ChannelFactory and others as well.

Typical here-be-dragons pattern

<pre><code>using (WCFServiceClient c = new WCFServiceClient())
{
 try
 {
 c.HelloWorld();
 }
 catch (Exception ex)
 {
 // You don't know it yet but your mellow has just been harshed.

 // If you handle this exception and fall through you will still be cheerfully greeted with 
 // an unhandled CommunicationObjectFaultedException when 'using' tries to .Close() the client.

 // If you throw or re-throw from here you will never see that exception, it is gone forever. 
 // buh bye.
 // All you will get is an unhandled CommunicationObjectFaultedException
 }
} // &lt;-- here is where the CommunicationObjectFaultedException is thrown
</code></pre>

Proper pattern:

<pre><code>using (WCFServiceClient client = new WCFServiceClient())
{
 try
 {
 client.ThrowException();

 }
 catch (Exception ex)
 {
 // acknowledge the Faulted state and allow transition to Closed
 client.Abort();

 // handle the exception or rethrow, makes no nevermind to me, my
 // yob is done ;-D
 }
} 
</code></pre>

Or, as expressed in your question without a using statement,

<pre><code>WCFServiceClient c = new WCFServiceClient();

try
{
 c.HelloWorld();
}
catch
{
 // acknowledge the Faulted state and allow transition to Closed
 c.Abort();

 // handle or throw
 throw;
}
finally
{
 c.Close();
}
</code></pre>

blocks|key|3269201|text|在CompletedMethod.中放置一个try+catch块|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|3269202|举个例子：|3269203|...
geocodeService.ReverseGeocodeCompleted+%2B=+ReverseGeocodeCompleted(se,+ev);
geocodeService.ReverseGeocodeAsync(reverseGeocodeRequest);
}

++++private+void+ReverseGeocodeCompleted(object+sender,+ReverseGeocodeCompletedEventArgs+e)
++++{
++++++try
++++++++{
++++++++++++//+something+went+wrong+...
++++++++++++var+address+=+e.Result.Results[0].Address;

++++++++}
++++++++catch+(Exception)
++++++++{+//+Catch+Exception
++++++++++++Debug.WriteLine("NO+INTERNET+CONNECTION");
++++++++}|code-block|syntax|javascript|3269204|entityMap^0|1|F|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|S|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

Place a try catch block in the CompletedMethod.

An Example:

<pre><code>...
geocodeService.ReverseGeocodeCompleted += ReverseGeocodeCompleted(se, ev);
geocodeService.ReverseGeocodeAsync(reverseGeocodeRequest);
}

 private void ReverseGeocodeCompleted(object sender, ReverseGeocodeCompletedEventArgs e)
 {
 try
 {
 // something went wrong ...
 var address = e.Result.Results[0].Address;

 }
 catch (Exception)
 { // Catch Exception
 Debug.WriteLine("NO INTERNET CONNECTION");
 }
</code></pre>

I have created a WCF service and client and it all works until it comes to catching errors. Specifically I am trying to catch the <code>EndpointNotFoundException</code> for when the server happens not to be there for whatever reason. I have tried a simple try/catch block to catch the specific error and the communication exception it derives from, and I've tried catching just Exception. None of these succeed in catching the exception, however I do get 

<blockquote>
 A first chance exception of type
 'System.ServiceModel.EndpointNotFoundException'
 occurred in System.ServiceModel.dll
</blockquote>

in the output window when the client tries to open the service. Any ideas as to what I'm doing wrong?

WCF/C# Unable to catch EndpointNotFoundException

服务器

调试器

我已经创建了一个WCF服务和客户端，它一直工作到捕获错误为止。具体地说，我正在尝试捕捉服务器由于某种原因而恰好不在那里时的EndpointNotFoundException。我已经尝试了一个简单的try/catch块来捕获特定的错误和它所派生的通信异常，并且我尝试只捕获异常。这些方法都不能成功捕获异常，但是我得到了在S...

问WCF/C#无法捕获EndpointNotFoundException
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