On a thread that is processing new data in the system, if the data is invalid I write a message in the event log, containing the Environment.StackTrace information.
Writing in the event log throws an exception with no text message
Message:
CallStack - at System.Environment.GetStackTrace(Exception e, Boolean needFileInfo)
at System.Environment.get_StackTrace()
at <my method that writes in the event log>
Any ideas why this happens?
EDIT: I am interested in what can cause the Environment.StackTrace to throw exception in general, so that i can understand what is happening in my case
#anchandra I don't know if you have figured this out since, as this is now 4 years old.
However I would like to add as I just stumbled upon this myself.
So, why does Environment.StackTrace throws an exception?
First the most uninteresting answer:
As you can see in the MSDN reference to the property, it can throw an ArgumentOutOfRangeException if "The requested stack trace information is out of range.", note also that the executing context must have System.Security.Permissions.EnvironmentPermission.
Now what stumped me for a second:
It does NOT throw an exception! Yes, that is what was happening to me, it actually returned me a Stack Trace that started listing the call to Environment.StackTrace like "at System.Environment.get_StackTrace()" then it showed all the other calling methods.
Because I was logging this into an audit log, if you look at it you assume there is an exception occurring at the last frame of the stack, but that's not true, I was just happening to request a Stack Trace at that point and stick it in my error log, very dumb once I realized this.
You need to capture the stacktrace before moving onto a separate thread.
Stacktrace will only show you the frames up to the root of the thread.
Related
Question 1 - practical
I run child process in my C# application using System.Diagnostics.Process. Like the following:
Process process = new Process();
// ... StartInfo initialization here
int timelimit_ms = 30000;
process.Start();
if (!process.WaitForExit(timelimit_ms))
{
// What exception to throw here?
throw new Excpetion(
"An executing method exceeded the time limit of " + timelimit_ms.ToString() + "ms");
}
I'm currently throwing System.ComponentModel.Win32Exception. But I don't sure it is the best choice. The child process is a simple command line utility. So the first question, what exception to throw in this situation?
Question 2 - thoretical
This is not the first time I ask myself about what exception to throw. And I don't know of a simple guidelines on how to pick a certain one. There are so much exceptions in C#, deeply inherited from one namespace to another. The second question, how to decide what exception to throw in a specific situation?
Practically, I'd throw a TimeoutException as it describes what is happening
Theoretically, if a quick google / read of the docs doesn't throw up an exception that already describes what is happening then you can just extend Exception to generate a WeirdThingThatHappensSometimesInMyApplication Exception.
But it depends who or what is going to "read" your exception. If your exception isn't exceptional then maybe you should do things differently :-)
how about a timeout exception?
I would think about throwing InvalidOperationException from the code.
As states MSDN, this exception is:
The exception that is thrown when a method call is invalid for the
object's current state.
So the caller of the function or consumer of the object that runs and waits for the process will be notified about the fact that execution of the function failed.
If you want to be detailed about declaration of the failure reason, you can express it
or in detailed message (if it's enough)
or create yuor own custom exception derived from InvalidOperationException and populate it with additional data you may need outside from the caller.
I'm receiving an unhandled exception while debugging, and the program stops executing. The debugger doesn't show me the line so I don't know what to fix.
An unhandled exception of type 'System.AggregateException' occurred in mscorlib.dll
Additional information: A Task's exception(s) were not observed either by Waiting on the Task or accessing its Exception property. As a result, the unobserved exception was rethrown by the finalizer thread.
Cannot obtain value of local or argument '<this>' as it is not available at this instruction pointer, possibly because it has been optimized away. System.Threading.Tasks.TaskExceptionHolder
How can I troubleshoot this problem?
I also found this question which is pretty similar.
As the message says, you have a task which threw an unhandled exception.
Turn on Break on All Exceptions (Debug, Exceptions) and rerun the program.
This will show you the original exception when it was thrown in the first place.
(comment appended): In VS2015 (or above). Select Debug > Options > Debugging > General and unselect the "Enable Just My Code" option.
You could handle the exception directly so it would not crash your program (catching the AggregateException). You could also look at the Inner Exception, this will give you a more detailed explanation of what went wrong:
try {
// your code
} catch (AggregateException e) {
}
The accepted answer will work if you can easily reproduce the issue. However, as a matter of best practice, you should be catching any exceptions (and logging) that are executed within a task. Otherwise, your application will crash if anything unexpected occurs within the task.
Task.Factory.StartNew(x=>
throw new Exception("I didn't account for this");
)
However, if we do this, at least the application does not crash.
Task.Factory.StartNew(x=>
try {
throw new Exception("I didn't account for this");
}
catch(Exception ex) {
//Log ex
}
)
In my case I ran on this problem while using Edge.js — all the problem was a JavaScript syntax error inside a C# Edge.js function definition.
im using the following pattern for translating win32 exceptions into .NET exceptions.
var result = A_KERNEL32_PINVOKE_CALL();
if (result == 0)
{
Marshal.ThrowExceptionForHR(Marshal.GetHRForLastWin32Error());
}
For completeness the pinvoke call is one of the following: LoadLibrary, GetProcAddress, SetWindowsHookEx.
This works well most of the time, throwing exceptions like this one:
System.ArgumentException: Argument out of range.
at System.Runtime.InteropServices.Marshal.ThrowExceptionForHRInternal(Int32 errorCode, IntPtr errorInfo)
But sometimes I get the following exception:
System.NotSupportedException: This Stream does not support seek operations.
at System.Net.ConnectStream.get_Position()
at System.Net.WebClient.WebClientWriteStream.get_Position()
at System.Drawing.UnsafeNativeMethods.ComStreamFromDataStream.Seek(Int64 offset, Int32 origin)
at System.Runtime.InteropServices.Marshal.ThrowExceptionForHRInternal(Int32 errorCode, IntPtr errorInfo)
I can't think of a reason for this exception. Please note that the stack trace doesn't start with ThrowExceptionForHRInternal like the first exception. Hence I think this might be a exception of the ThrowExceptionForHR method itself.
EDIT: Please note that I'm not calling any Stream methods directly. However the code is executed in a thread pool thread, so there might be other code in the same thread using Stream methods.
Any suggestions how to solve this issue?
UPDATE: I just found out, that the stack trace
at System.Net.ConnectStream.get_Position()
at System.Net.WebClient.WebClientWriteStream.get_Position()
at System.Drawing.UnsafeNativeMethods.ComStreamFromDataStream.Seek(Int64 offset, Int32 origin)
belongs to a call to Image.Save(Stream, Format). There a the NotSupportedException is caught. These code peaces are completely independant, but maybe they are executed on the same thread pool thread.
So why does this exception influence my code in another method?
By now I think, that I misused the Marshal.ThrowExceptionForHR() method. I suppose that it's not intended to be used with a Win32 call. My interpretation of the behavior is, that the function uses context information of the current thread to gather more details about the exception. See this blog for a similar problem.
In my case the issue can be solved by creating my own ThrowExceptionForWin32ErrorCode(errorCode) method.
Please keep answering, if you got a better solution.
I don't know why ThrowExceptionForHRInternal tries to manipulate some stream.
While call stack looks strange, consider not passing stream directly from Web response to drawing functions which seem to cause exception in your case but copy data to memory stream first. This will likely allow you to see what original problem is (as ThrowExceptionForHRInternal will no longer fail trying to manipulate a stream).
I have an unusual case where I have a very simple Exception getting thrown and caught in the same method. It isn’t re-thrown (the usual kind of problem naïve programmers have). And yet its StackFrame contains only one the current method. Here’s what it looks like:
at (my class).MyMethod() in C:\(my file path and line)
In reality there are probably 30 methods leading up to this in the VS2010 debugger's call stack, going across half a dozen different assemblies. It seems impossible for all that to have been optimized out. Moreover, this code is built in debug mode, without optimizations, for .NET 4. I even have (based on http://msdn.microsoft.com/en-us/library/9dd8z24x.aspx) .ini files (including one named [app].vshost.ini) in the same folder containing:
[.NET Framework Debugging Control]
GenerateTrackingInfo=1
AllowOptimize=0
Also, the method calls are not at the end of methods, so tail-recursion optimization seems further unlikely.
As to how it is called: there are no uses of reflection on the call stack, no Invoke() or BeginInvoke() of any kind. This is just a long chain of calls from a button click. The click handler is about 10 calls down the call stack. Beneath that you have the usual WndProc, NativeWindow.Callback, native/managed transitions, and message loop. This is ultimately inside a ShowDialog() call which is run from a C# EXE assembly.
Now, I found that I can construct instances of the StackTrace class in my catch handler, and if I pass the Exception object, the call stack is also short. If instead I just call new StackTrace() with no arguments, it yields a complete call stack.
I’ve used Reflector in an attempt to debug into the internals of the Exception class getting thrown and its call stack constructed, but I couldn’t set breakpoints in Exception or in StackTrace. I could set them in Environment.GetStackTrace() and this method (which Exception calls) does not appear to get called during the construction and throwing process, but I don’t know if the debugger is really working properly. (This method does get triggered for some other things though, so I'm not sure what to make of it.)
Here’s an excerpt of the method:
private void MyMethod()
{
...
try
{
throw new ApplicationException("Test failure");
}
catch (Exception e)
{
StackTrace stackTrace1 = new StackTrace(e);
StackTrace stackTrace2 = new StackTrace(e, false);
StackTrace stackTrace3 = new StackTrace(e, true);
StackTrace stackTrace4 = new StackTrace();
string STs = stackTrace1.ToString() + "\n---\n"
+ stackTrace2.ToString() + "\n---\n"
+ stackTrace3.ToString() + "\n---\n"
+ stackTrace4.ToString();
Log(EventSeverity.Debug, STs);
...
}
}
It’s really pretty simple: Throw exception, catch and log it.
I get the same results either in the debugger or when running standalone—a one-line call stack. And I know I have seen this problem elsewhere in our code base. Previously I had assumed it was due to re-throwing exceptions, but in a lot of cases it we log right inside the initial catch block. I’m quite baffled and all the web searching I’ve done hasn’t produce anything.
This is a little too much to add as a comment to the answer provided, but here's some more information:
I now see that this behavior is discussed at
http://dotnetthoughts.wordpress.com/2007/10/27/where-did-my-exception-occur/ and that it is actually described at http://msdn.microsoft.com/en-us/library/system.exception.stacktrace.aspx (though I think one could easily miss what they're saying there).
So I guess my "solution" will be a little hit-or-miss. We have a central method we usually call to format exceptions. Inside that method, I'll create a new StackTrace() both with and without the Exception object. Then I'll look for the method that is at the bottom of the Exception's stack trace, and display everything beneath that in the new StackTrace(), indicating it was called by that series of calls.
The down side of course is that if this method isn't used, the information won't be there. But I had to expect some kind of code change somewhere.
When an exception is thrown, only a partial stack trace will be used in the Exception.StackTrace property. The stack only shows calls up until the method that is catching the exception. To get the full stack (as you have noted) you should create a new StackTrace() object.
I can't find any links on it at the moment but I believe the stack trace is built by walking up the stack while throwing the exception. Once the exception reaches a catch block, the stack stops being compiled. Therefore, you only get a partial stack.
Typically, a catch block is not concerned with who called it, but where the exception is originating from.
I'm reading a foreign source code and there occurs sometimes a
NullException
by Drag'n'Drop operation. The problem is, that all parameters are never null, so I'd like to be able to debug this method somehow.
Any ideas ?
Any exception thrown while a drag+drop is in progress is swallowed by a catch all handler in DoDragDrop. You can see the first-chance exception in the Output window but that's all. To get the debugger to stop use Debug + Exceptions, tick the Thrown checkbox on CLR exceptions.
OK !
It seems that the Call Stack in Message Details helps to locate the problem.
Anyways.. for me it's sufficient.