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I am dealing with a puzzling situation here,and need any help I can get . I am using Visual Studio 2008 and have a dev site running on IIS. When I Attach to the process running in IIS, it attaches successfully(no errors). However when I attempt to debug, nothing happens. I have closed out my browser, done a restart on the application pool, and website, cleared cache, and even forced a rebuild in visual studio. Still I am unable to step into code. Any idea what I could have wrong here?
The breakpoint will not currently be hit. No symbols have been loaded for this document.
Your symbols might be wrong or missing. In extra rare circumstances you might need to step inside the function via assembly, only then VS picks up that you're actually calling your component.
Check if you have you set compilation debug=”true” in you web.config file?
I believe you need to debug the website from within Visual Studio in order for breakpoints to be hit. Use the green "play" button, or use F5, or just go to Debug > Start Debugging.
I am working on a C#.NET class library project in VS2010. In my project settings -> debug settings, I have the project set to start an external program (C:\Windows\SysWOW64\wscript.exe) which runs a very simple jscript file (test.js). The script simply creates an instance of the class and calls one of it's methods.
The problem is when I start debugging, VS2010 does not stop at any of my breakpoints. If I open up the exact same project in VS2008 it does stop at the break points. Is there a new setting somewhere that is preventing the breakpoints from being hit? Has anyone else ran into this issue?
My first check would be to disable "Just My Code"
Tools -> Options
Debugger
Uncheck "Enable Just My Code"
Try the scenario again.
To solved this problem by creating a config file for the application which is using the component to debug with the following data:
<?xml version="1.0"?>
<configuration>
<startup>
<supportedRuntime version="v2.0.50727"/>
</startup>
</configuration>
With this file you tell the debugger to use the right runtime version for debugging (it seems the debugger uses version 4.0 by default).
I have a tried a whole day to find out why I couldn't debug my visual studio 2012 console application, and the answer was embarrassing.
I was running it in "RELEASE" mode.
Sometimes the obvious is the hard to find.
Close the Visual Studio IDE and Open it. Now it will work. For me it also face the same issue. I used this way to overcome
I had a "Rebuilt" VS2013 project that I couldn't debug (no symbols). Finally, I saw Optimization was checked (Project->Properties->Build). I unchecked it and Rebuilt. Symbols loaded finally. My two cents, only use (compile) Optimization when absolutely necessary.
While I can't answer why it happens, I can provide you with workaround.
Include
using System.Diagnostics;
At the very beginning of your code (Class constructor for instance) place the following lines:
#if (DEBUG)
while(!Debugger.IsAttached);
Debugger.Break();
#endif
Start debugging.
Menu Tools→Attach to Process
Attach to your process.
breakpoint should trigger in your code.
Other breakpoints should trigger as well.
Could be a number of reasons. Usually it's because you're trying to debug against the wrong version.
These actions work about 80% of the time.
Get the latest code
Clean
Rebuild
Restart IIS
Try again
If no good, go to Debug > Windows > Modules and if the relevant dll is there, right click it and load symbols.
If it's not in the list, try running the code anyway. Sometimes even though it says the breakpoint will not be hit, it's only because the dll is not loaded until you enter a scenario that needs it. Try the scenario that depends on the dll, and it may just hit the breakpoint anyway.
Oh one more idea, restart your browser. You might have something cached from an older dll.
If the reason is wrong .NET runtime version (which was my problem), instead of creating configuration file you can simply choose the right version in the Attach to process dialog.
In the dialog, next to Attach to click on Select and switch from Automatically... to Debug these code types where you should check the right version.
If this was your problem also, then you probably had "Symbols not loaded" message on your breakpoints. Immediately after selecting the right version you should see that this error is no longer reported.
For me it was fixed by:
Open the project properties is VS2010
Goto Compile -> Advanced Compile Options
Change 'Generate debug Info' from 'None' to 'Full'
The problem could be your browser is using a cached version of the page, you are working with.
Try to add som nonsense extra querystring in your adress line of the browser f.x. add ?NONSENSE=1234
This forces the browser to use a new version of the web page since it does not know if the page should look different with this Query in the end. Next time use ?NONSENS=1235.
I had a problem with misplaced breakpoints in my native c++ code.
The reason was I had been editing the code so some line ends in the code was not \r\n. It was not possible to see in the code unless you searched for \r\n.
After inserting the proper line ends \r\n the debugger worked.
I encountered the similar issue but its in a CLR project. I had some old c++ syntax in the CLR project. For me after I enabled 'Use managed compatibility mode' in Tools>options>Debugging>General it started to hit the break points.
Even if I create a clean WinForms project, Edit and Continue doesn't work and gives me the error:
Changes are not allowed when the debugger has been attached to an already running process or the code being debugged was optimized at build or run time.
Edit and Continue option is checked in Tools → Options → Debugging.
Optimization is not enabled.
Seems like there is no any managed profiler set up.
I am running in Debug mode
I am running on x64 CPU and Windows XP 32-bit, but setting platform target to x86 rather than AnyCpu doesn't help.
Repairing Visual Studio installation doesn't help.
I also found this article on MSDN website:
Unsupported Scenarios
Edit and Continue is not available in the following debugging scenarios:
Debugging on Windows 98.
Mixed-mode (native/managed) debugging.
SQL debugging.
Debugging a Dr. Watson dump.
Editing code after an unhandled exception, when the "Unwind the call stack on unhandled exceptions" option is not selected.
Debugging an embedded runtime application.
Debugging an application with Attach to rather than running the application with Start from the Debug menu.
Debugging optimized code.
Debugging managed code when the target is a 64-bit application. If you want to use Edit and Continue, you must set the target to x86. (Project Properties, Compile tab, Advanced Compiler setting.).
Debugging an old version of your code after a new version failed to build due to build errors.
But I can answer "No" to every item in this list.
It worked before, but several days ago it stopped working, and I don't know what could be the reason.
Other Applicable Solutions:
Below is an incomplete, unordered list of possible solutions to try if you* are trying to fix Edit & Continue quickly.
Make sure you are in Debug Mode
Make sure you're not launching a mixed mode process
Try to set the CPU target to x86 rather than AnyCPU (on x64 machines)
Uncheck the Optimize Code checkbox for Debug Mode in Project Properties->Debug
Uncheck the Optimize Code checkbox in Project Properties->Build
Uncheck Enable Optimizations in Advanced Compiler Settings
(ASP.NET) Check nightcoder's answer if it is the case
(ASP.NET) Check this answer (by matrixugly) if it is the case
(ASP.NET) Ensure you have Edit and Continue enabled on the Web tab (vs2010)
(ASP.NET) Go to Properties > Web > Servers, and make sure that Enable and continue is checked under Use Visual Studio Development Server.
(ASP.NET WebAPI) Make sure you've stopped in the Controller's method using a breakpoint, before trying to edit it.
(vs2017) Go to Tools > Options > Debugging and uncheck (deselect) 'Edit and Continue'. This is actually the opposite of the 'conventional' advice (see some other points in this post). It does not allow you to actually make changes in your running program (i.e. it does not hot-swap the code changes that you make) - it simply allows you to edit your code (i.e. it prevents that annoying message and "locking" your editor).
Go to Tools > Options > Debugging > General and make sure Require source files to exactly match the original version is unchecked.
Check Enable Windows debug heap allocator (Native only) [VS Community 2017]
Are you using Microsoft Fakes? It inhibits Edit & Continue.
Kill all the *.vshost.exe instances by selecting End Process Tree in the Task Manager. VS will regenerate a correct instance.
Remove all the breakpoints with Debug->Delete All Breakpoints
Enable and Continue exists in both the Tools > Options > Debugging menu and also in the Project Settings. Be sure to check both places. edit & Continue is not supported with the extended Intellitrace setting.
Be sure Debug Info in Project Properties > Build > Advanced > Output > Debug Info is set to Full
Some plugin may be interfering. Check by disabling/uninstalling and then trying again the other solutions.
If you're not paying enough attention, the error you get while trying to fix this may change to something else that is easier to diagnose. E.g. A method containing a lambda expression cannot support edit and continue.
Make sure the System variable COR_ENABLE_PROFILING is not set to 1. Some profilers set this when installing and leave it like that after uninstalling. Open a command prompt and type set to quickly check it your system is affected, if so remove the variable or set it to 0:
In Windows 8 and above, search for System (Control Panel).
Click the Advanced system settings link.
Click Environment Variables.
Remove COR_ENABLE_PROFILING
Be aware of unsupported scenarios (as reported in the question) and that unsupported edits.
* by 'you', I mean the visitor of the page who is hammering his head on a keyboard to find The solution.
Feel free to edit this answer to add your workaround if not listed here!
If you're debugging an ASP.NET application, go to properties > web > Servers, and make sure that "enable and continue" is checked under Use Visual Studio Development Server.
I finally got to solve the problem: UNINSTALL Gallio
Gallio seems to have quite some many rough edges and it's better to not use MbUnit 3.0 but use the MbUnit 2.0 framework but use the gallio runner, that you are running without installing from the installer (which also installed a visual studio plugin).
Incidentally, I had the issue even after "disabling" he Gallio plugin. Only the uninstall solved the problem.
PS. Edited by nightcoder:
In my case disabling TypeMock Isolator (mocking framework) finally helped! Edit & Continue now works!!!
Here is the answer from TypeMock support:
After looking further into the edit
and continue issue, and conversing
about it with Microsoft, we reached
the conclusion it cannot be resolved
for Isolator. Isolator implements a
CLR profiler, and according to our
research, once a CLR profiler is
enabled and attached, edit and
continue is automatically disabled.
I'm sorry to say this is no longer
considered a bug, but rather a
limitation of Isolator.
I had the same problem. I even re-installed VS 2008 but the problem did not go away. However, when I deleted all the break points then it started to work.
Debug->Delete All Breakpoints
I think it was happening because I had deleted an aspx page that had break points in its code, and then I created another page with the same name. This probably confused the VS 2008.
"Edit and Continue", when enabled, will only allow you to edit code when it is in break-mode: e.g. by having the execution paused by an exception or by hitting a breakpoint.
This implies you can't edit the code when the execution isn't paused! When it comes to debugging (ASP.NET) web projects, this is very unintuitive, as you would often want to make changes between requests. At this time, the code your (probably) debugging isn't running, but it isn't paused either!
To solve this, you can click "Break all" (or press Ctrl+Alt+Break). Alternatively, set a breakpoint somewhere (e.g. in your Page_Load event), then reload the page so the execution pauses when it hits the breakpoint, and now you can edit code. Even code in .cs files.
Couple of things to check
Make sure your compile is set to Debug vs. Release
Make sure you're not launching a mixed mode process
If on a 64 bit machine Make sure to set the CPU target to x86 rather than AnyCPU
EDIT
I don't believe this should matter but make sure that the hosting process is enabled for the target platform. Probably won't help.
If it repros for new projects then it might be something even more subtle. I would try the following.
Backup HKCU:\Software\Wow6432Node\VisualStudio\9.0 (maybe just rename it)
Delete the same key
Try the repro again
None of the above solutions worked for me(running on a 64x machine).
Finally I clicked on 'advanced compiler settings' and UNCHECKED 'enable optimizations' and I can now step through code and edit while debugging.
For me, for a reason that I don't understand, the setting "Generate debug info" in the "Advanced Compiler Settings" was set to "pdb-only" instead of "Full".
By default, this parameter is always set to "Full" but a mysterious poltergeist has changed this parameter on last night. :)
P.S. I'm in Visual Basic .Net with Visual Studio 2010
If your concern is with an ASP.NET app, ensure you have edit and continue enabled on the web tab (vs2010). There was also a separate setting for ASP.NET debugging in earlier versions.
Regards,
Adam.
I found that even though under project properties build & debug tab are set to Debug and all the other setting are correct I still get the message, however after digging some more
under the Build menu select Configurations Manager... and make sure Debug is selected in two places there as well. go figure...how many different places do they need to set debug?????? even though you set Project - Configuration to Debug then under Build - Manager it is not changed so you have change the same setting there as well Project Configuration - seems like a microsoft issue again.......
This problem is due to Intellitrace setting
If Intellitrace is enabled make sure Intellitrace event only is checked
Otherwise this will not allow edit and continue..
If you will click on Intellitrace options you will see the warnings.
Following shooting helped me using VS2010:
go to Tools, Options, Debugging, General and make sure "Require source files to exactly match the original version" is unchecked.
That happens when the debugger hasn't hit a breakpoint or you haven't hit Break All (pause). It couldn't be that simple could it?
The error says a possible cause is: "the code being debugged was optimized at build or run time". Go to Project Properties->Debug and uncheck the Optimize Code box for Debug mode.
I had this problem in Microsoft Visual Studio 2008 and the solution is easy. when you run your project please set in "Debug" mode not "Release". The another people solution can be useful.
If I create a new project, edits while debugging do not work. If I create a new website, edits while debugging work as expected.
I ran into this today - turns out that having Debug Info set to pdb-only (or none, I'd imagine) will prevent Edit and Continue from working.
Make sure your Debug Info is set to "full" first!
Project Properties > Build > Advanced > Output > Debug Info
In my case just reseting to default debugger settings and setting IntelliTrace-> only intellytrace events helps
Some things that seemed to help using VS2010:
go to Tools, Options, Debugging, General and make sure "Require source files to exactly match the original version" is unchecked.
multiple .vshost.exe instances can be left over from e.g. detaching the VS debugger from a stopped process. This will interfere with breakpoints and compiles as well. Use Task Manager, Processes tab to kill all instances of .vshost.exe by right-clicking each instance and selecting End Process Tree. VS will create a new instance.
I removed a dataset from my project because I didn't use it. After that I could modify the program when debugging.
I did all the changes mentioned in every other answer and none worked. What did I learn? Enable and Continue exists in both the Tools > Options > Debugging menu and also in the Project settings. After I checked both, Enable and Continue worked for me.
Seems illogic, but only way was disabling edit and continue from VS 2017 options... Then AspNet edit and continue began to work...
what worked for me was unchecking "Use Managed Compatibility Mode" under
Tools -> Options -> Debugging
TBN: checking or unchecking "Require source file to exactly match the original version" seems not influences the E&C
Hope this can help.
Enable edit and Continue only work run IIS Express.
Don't work in Local ISS or External Host.
I'm adding my answer because the thing that solved it for me isn't clearly mentioned yet. Actually what helped me was this article:
http://www.rubencanton.com/blog/2012/02/how-to-fix-error-changes-are-not-allowed-while-code-is-running-in-net.html
and here is a short description of the solution:
Stop running your app.
Go to Tools > Options > Debugging > Edit and Continue
Disable “Enable Edit and Continue”
Note how counter-intuitive this is: I had to disable (uncheck) "Enable Edit and Continue".
This will then allow you to change code in your editor without getting that message "Changes are not allowed while code is running".
Note however that the code changes you make will NOT be reflected in your running program - for that you need to stop and restart your program (off the top of my head I think that template/ASPX changes do get reflected, but not VB/C# changes, i.e. "code behind" code).
I install the stackify, when i enable this on icon tray, it stop my debugging with edit, so i found
Close the visual studio , in my case its vs2017
Go to icon tray and right click on stackify icon and disable .NET Profiler
Open Visual studio run application again in debug mode with debugger and it allow me edit while debugging
I had this annoying issue since I upgraded my VS 2019 to 16.4.3 and caused me a lot of headache.
Finally I solved the problem this way:
1. Stop Debugging
2. Select the solution from "Solution Explorer"
3. In the Properties window change the "Active config" Property From "Release|Any CPU" To "Debug|Any CPU"
4. In Debug > Options > General Check the Edit and Continue checkbox
That worked for me, and hope it works for you too.
embed interop types visual studio should be set to false
I had this happen in a linked class file. The rest of the project allowed E&C, but I got the same error editing the linked file. Solution was to break linked file into it's own project and reference the project.
I faced the same problem. My problem was that I could modify a file, but not another (both are in same project). Later I found that the file I couldn't modify was also part of another project. That another project (Unit Test) wasn't loaded, and intelligent VS debugger shows the error that assembly for this given file was not loaded, and changes aren't allowed. How weird!
Hence, I had to unload the unit-test project and continue the EnC debugging.
In my Visual Studio instance, even if I just wrote a single line of return in a C# console application, it will take me a minute after pressing F5 to execute the actual code (I mean the time it takes to stop on the single return statement after pressing F5 -- I set a breakpoint on the return statement in the main function). What is wrong? Is there a check list?
I am using Visual Studio 2008 VSTS edition and debugging on Windows Server 2003 x64.
You may need to delete all your breakpoints---note that you need to click the "Delete all breakpoints" button (or use Ctrl + Shift + F9), NOT just delete them one by one. If Visual Studio has mangled your solution settings the latter will not work. You may need to add a breakpoint first, in order for this to work (clever, eh?).
If worst comes to worst, you may need to delete your .suo file and let Visual Studio start a new one from scratch. Note that you will lose your personal solution configuration settings, however (only for this solution, not any others). However, you may want to move/rename the file temporarily until you determine whether or not this is the problem; that way, you can always move it back. I have seen some online resources recommend deleting (moving/renaming) the .ncb file as well.
I have seen this before. Try deleting all your breakpoints and then set the ones you want. Hit F5. Is it faster now?
I just noticed that you mentioned setting up the .NET source debugging feature. Try to disable that. Your network connectivity to Microsoft's source server may be slow. Also disable any symbol server connectivity in menu Tools → Options → Debugging → Symbols.
Also try disabling "Enable property evaluation and other implicit function calls" in menu Tools → Options → Debugging → General.
Or remove your .suo file which can be found next to your solution (.sln) file.
This solved an issue I had with debug sessions taking a long time to start and stop.
I had this problem. After trying all the listed advice and removing all Visual Studio extensions, we finally figured out that somehow IntelliTrace was enabled. Disabling that fixed everything.
How to: Enable and Disable IntelliTrace
Do you have a lot of breakpoints set? Those can really slow down startup time. Everytime a new module is loaded into the process address space, they all need to be checked to see if they are valid.
Go to menu Tools → Options → Debugger → Symbols and check if you have public symbols set or UNC network paths set. Also check menu Tools* → Options → Debugger → General to see if you have source server set.
All of these can affect debugging based on slow network speed or unavailable servers. The 5 minute wait time is network timeouts.
If nothing in options is set, check to see if you have the _NT_SYMBOL_PATH environment variable set.
My colleague had a very slowly responding Visual Studio, and it literally took minutes to perform a step while debugging.
The root cause turned out to be an anti virus program (Threatfire) that went crazy while Visual Studio was running. Killing its process immediately fixed everything.
In my case changing the debug symbol "Automatically load symbol for" option from "All modules" to "Only specified modules" solved the problem. You can change this option from menu Tools → Options → Debugging → Symbols.
A different cause plus... How to find the problem
To me it was the option ShowOtherThreadIpMarkers. A value of 1 makes Visual Studio (2010) unbearably slow (3-5 seconds for each debug step. With a value of 0, it is fast again.
What is it that option? I have no idea. I could not find it through the Visual Studio user interface.
I unchecked all possible debugging options in there and nothing worked.
So I went to Import/Export Settings and loaded my old settings I've previously saved going backward in time until Visual Studio was fast again, then compared the vssettings files..., etc., etc.
I'd like to remark that if you load the settings while you are in debug mode stopped on a breakpoint, they become effective immediately. You don't have to stop the debugger and restart.
From ScottGu's blog linked by Travis: "One other performance gotcha I've heard about recently is an issue that a few people have reported running into with the Google Toolbar add-in. For some reason this can sometimes cause long delays when attaching the Visual Studio debugger to the browser. If you are seeing long delays with your web application loading, and have the Google Toolbar (or other toolbars) installed, you might want to try uninstalling them to see if that is the cause of the issue."
Running under the debugger for me was roughly 10x slower than running without debugging.
After trying every solution suggested here, I went through every debugger setting and enabled/disabled to see if it made a difference.
For me, it turned out that disabling Suppress JIT optimization on module load in the debug settings massively improved things.
Make sure you don't have any stale network mappings to servers that no longer exist (network timeouts will kill you). Or use something like Process Monitor to see if a network (or other file error) seems to be blocking for a long time.
Are you using a symbolsServer to download symbols for Windows DLL files?
If so, disable that as it can take some time, but I wouldn't expect that to cause long delays in a basic console application.
Menu Tools → Options → Debugging → Symbols.
I know this is an old topic, but for what it's worth...
I've found that if I've had a separate Internet Explorer window open for a long time it can take up to a minute to start debugging. Close all Internet Explorer windows and debugging starts immediately.
In my case Google Toolbar was slowing down my debugging.
gplus_notifications_gadget.html just kept going on and on overloading the debugger. I wanted to keep the Google Toolbar because I use it on a regular basis, so I just disabled the G+ notification button (the small button besides the profile button). It is happy now.
I had the same issue in Visual Studio 2010, with stepping in the code excruciatingly slow (between 3 to 10 seconds). However, none of the above settings modification did the trick.
I eventually found the ultimate solution, which would work in all of the above post issues: reset all your settings, as described here (essentially menu Tools → Import and Export Settings, Reset all settings, with saving existing settings to a file (for reverting)).
You may first want to save a particular part of your settings. For instance, I first saved my color theme (Solarized-like) and then restored it after the global reset.
For me, the setting that killed performance (Windows 8 even hanged except for mouse movement) was to uncheck "Break all processes when one process breaks" in menu Options → Debugging → General.
Just one more cause of a slow Visual Studio debugging experience...
Long time ago I enabled FusionLog to see what was causing an assembly binding problem.
Make sure you disable it after using it. Why? Because it writes a lot of logging data to the disk while enabled.
This is the FusionLog key on Window's Registry (regedit.exe):
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Fusion
Change the ForceLog, LogImmersive and LogResourseBindings values from 1 (enabled) to 0 (disabled).
I had this problem too, but it had nothing to do with breakpoints in my case. It was code shortcuts that I added in the tasks window:
http://www.customsoftwareframeworks.com/blog/longwaittimetoinsertoraddalineoftextbuginvisualstudio--tasklistwindow--onlywhenaddingandremovelines
I'm sure there are other ways you could see a problem like this, but there is a bug somewhere that caused this problem for me...deleting all my options would have fixed this, but that is something that I did not want to do. So, I debugged it and wrote about it in my blog...your problem sounds like mine.
Something that has worked for me is to make sure there are no conditional break points. Other than that, I have had success fixing slow debugging by simply restarting Visual Studio and only opening one instance of Visual Studio at a time.
I had a similar issue and none of the other guidance seemed to help. I had rebooted to no avail. I had removed all breakpoints, deleted the .suo file, checked that symbols weren't being loaded from external sources, and checked that no paths existed in the application that was unavailable.
Then, I thought to clean the solution. I noticed in the output window that C# IntelliSense reported an issue when cleaning:
There was a problem reading metadata
from
'{B0C3592F-F0D1-4B79-BE20-3AD610B07C23}'
('The system cannot find the file
specified.'). IntelliSense may not
work properly until the solution is
reloaded.
In this case, once you actually discover the error message, it tells you exactly how to resolve it. (Good job on the error text, poor job on discoverability!) I unloaded the solution's projects, then reloaded them. I was then able to successfully run clean solution. It worked, and the debugger did as well.
Closing the "Autos" window improved debugging for me in Visual Studio 2008 for a big native C++ solution.
Hiding it won't work. It needs to be closed.
I experienced the same slowdown and disconnecting from the network fixed the problem for me as some other comments and answers have stated (but of course that is not an ideal fix).
For my case this one simple change fixed my solution: In the project properties on the debug tab I disabled "Enable the Visual Studio hosting process" (I am running Visual Studio 2010).
Get more memory and a faster HD. More details are here.
Is there a good way to debug errors in the Visual Studio Designer?
In our project we have tons of UserControls and many complex forms. For the complex ones, the Designer often throws various exceptions which doesn't help much, and I was wondering if there's some nice way to figure out what has gone wrong.
The language is C#, and we're using Visual Studio 2005.
I've been able to debug some control designer issues by running a second instance of VS, then from your first VS instance do a "Debug -> Attach to Process" and pick "devenv".
The first VS instance is where you'll set your breakpoints. Use the second instance to load up the designer to cause the "designer" code to run.
See Debugging Design-Time Controls (MSDN).
It has been a pain in 2005 and still is in 2015. Breakpoints will often not hit, probably because of the assemblies being shadow copied or something by the designer(?). The best you can do is to break manually by introducing a call to Debugger.Break(). You may wrap it into a compiler conditional as so:
#if DEBUG
System.Diagnostics.Debugger.Break();
#endif
int line_to = break; // <- if a simple breakpoint here does not suffice
I have had this happen many times and it is a real pain.
Firstly I'd suggest attempting to follow the stack trace provided by the designer, though I found that often simply lists a bunch of internals stuff that isn't much use.
If that doesn't work then try compiling and determining the exception from there. You really are flying blind which is the problem. You could then try simply running the code and seeing what exception is raised when you run it, that should give you some more information.
A last-gasp approach could be to remove all the non-generated code from the form and gradually re-introduce it to determine the error.
If you're using custom controls you could manually remove the generated code related to the custom controls as well if the previous method still results in an error. You could then re-introduce this step-by-step in the same way to determine which custom control is causing the problem, then go and debug that separately.
Basically as far as I can tell there's no real way around the problem other than to slog it out a bit!
I discovered why sometimes breakpoints are not hit. In the Attach to Process dialog, "Attach to:" type has to be "Select..."'d.
Once I changed to "Managed 4.0, 4.5", breakpoints for a WinRT application were hit. Source: Designer Debugging in WinRT.
Each one is different and they can sometimes be obscure. As a first step, I would do the following:
Use source control and save often. When a designer error occurs, get a list of all changes to the affected controls that have occurred recently and test each one until you find the culprit
Be sure to check out the initialization routines of the controls involved. Very often these errors will occur because of some error or bad dependency that is called through the default constructor for a control (an error that may only manifest itself in VS)
You can run a second instance of VS and attach it to the first instance of VS (Ctrl+Alt+P). In the first instance set the breakpoints, in the second instance run the designer, and the breakpoint will fire. You can step through the code, but Edit-and-Continue will not work.
For Edit-and-Continue to work, set you control library's debug options to run a VS with the command line argument being the solution filename. Then you can simply set the breakpoints and hit F5. It will debug just like user code! As a side note, you can do this will VS and Office add-ins also.
This worked for me for Visual Studio 2022:
I opened a second Visual Studio instance
In the second instance I clicked Debug -> Attach to Process...
I selected DesignToolsServer from the process list
More details: https://learn.microsoft.com/en-us/dotnet/desktop/winforms/controls/walkthrough-debugging-custom-windows-forms-controls-at-design-time?view=netframeworkdesktop-4.8