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How do I disable threading and async for debugging in c# [duplicate]

I have a solution with some projects. There are several break-points in different projects. I want to trace the first thread hit one of these break-points and continue tracing that single thread despite of other threads entering the same code-blocks.
I know this is possible through defining a condition on the break-point, that is, thread name = ... or thread Id = ... but my case is a heavy loaded ASP.NET application and as soon as I attach to w3wp.exe many threads will hit the break-points. I need some thing like a ThreadLocal<break-point>.
Is it possible? If so, how?

Here's what I did:
Set a conditional break point that I
knew would only hit on the thread
that I was looking for.
Once the breakpoint hits and you are in the thread you want, in the Visual Studio Threads window (while debugging, Debug -> Windows -> Threads), Ctrl + A (to select all threads), and then Ctrl + click the thread you are currently on. You should have all threads except the one you want to debug selected.
Right-click, and choose "Freeze".
Now, Visual Studio will only step through the thawed thread. It seems to be much slower when doing this, presumably because it has to loop through all of the frozen threads, but it brought some sanity to my multi-threaded debugging.

Freeze/Thaw threads is an incorrect way because other threads don't execute any code.
The most correct and usable way is to:
Hit Ctrl+A in the breakpoints window (select all breakpoints).
Right click and select "Filter...".
Enter "ThreadId=(current thread id)".
In Visual Studio 2015 and newer, the process is similar:
Hit Ctrl+A in the breakpoints window (select all breakpoints).
Right click and select "Settings...".
Check "Conditions" and select "Filter" in the dropdown
Enter "ThreadId=(current thread id)".
So all threads are executed, but the debugger hits on the current thread only.

If multiple threads are being spawned as for a web application, #MattFaus answer's will not work. what I did instead is the following
Set up a breakpoint to interrupt the thread in the function I want.
Once the thread gets to the breakpoint and is paused, I remove the breakpoint and continue debugging using F8,F10 and F11, so that the others threads can run.

I have just released a Visual Studio 2010+ extension that does exactly what you are looking for.
And it's free :).
Presentation
This Visual Studio extension adds two shortcuts and toolbar buttons to allow developers to easily focus on single threads while debugging multi-threaded applications.
It dramatically reduces the need to manually go into the Threads window to freeze/thaw all threads but the one that needs to be followed, and therefore helps improve productivity.
Features
Restrict further execution to the current thread only. Will freeze all other threads. Shortcut: CTRL+T+T or Snowflake button.
Switch to the next single thread (based on ID). Will change current thread and freeze all other threads. Shortcut: CTRL+T+J or Next button.
Check it out here on the Gallery, on the official page or the Github repository.

A slightly different approach which I've used:
Create a normal breakpoint and let it get hit
Look in your threads window for the managed thread ID that you're current debugging
Right click your breakpoint in the breakpoints window and selecter filter
Enter ThreadId=xxx where xxx is the thread ID from 2
You can now debug without stopping other threads and without them hitting your breakpoint
This assumes you have time to do the above before a second thread hits your breakpoint. If not and other threads hit your breakpoint before you've done the above you can right click them in the threads window and choose freeze.

In VS 2019:
Set a breakpoint somewhere.
Hit F5 (Continue) until your thread comes.
Click on breakpoint to remove it.
You can step the thread with F10 or F11.

Set a Breakpoint Condition by right clicking the side bar of the line. Select "Condition" and enter the following with the name of your thread in quotes:
System.Threading.Thread.CurrentThread.Name=="name_of_your_thread"
Alternatively you can do the same by getting the thread's "Managed ID" from the "Threads" Window and use:
System.Threading.Thread.CurrentThread.ManagedThreadId==your_managed_thread_id

I would suggest adding another instance of the application on the live server, either on the same hardware or a new machine (cluster it) and then debug only that instance. I wouldn't add a breakpoint in code users are triggering. If that's not an option, I'd add more tracing.
However, if this is absolutely necessary and you need a solution stat, I'm sure you could add a breakpoint that breaks only if the request is coming from your IP address. You would do this by adding a conditional breakpoint that inspects HttpContext.Request.UserHostAddress. Note however that this slows down your application considerably.

If you don't want to stop all other threads (maybe you are attaching Visual Studio debugger to a running application that needs to answer to requests), you can use a macro that create and remove breakpoints automatically.
This is suggested in an answer to Stack Overflow question "Step over" when debugging multithreaded programs in Visual Studio.
However, the link only explain how to debug line by line. I suggest you modify the macro (if you're comfortable with it) to make it modify all breakpoints (in a given range of line for instance) to stop only on the current thread.

I think this is slightly different in Visual Studio 2015. They've changed a few things in the breakpoints, but here's how to apply the accepted answer from hzdbyte (above):
On the breakpoint in the coding margin, Right-Click > Conditions > Change from 'Conditional Expression' to 'Filter'. This then allows you to filter by ThreadId.
Alternatively on the breakpoint in the Breakpoints window, Right-Click > Settings > tick the Conditions box and do the above.

in VS2019, the conditional breakpoint is tid == xxxxx
this way the breakpoint will be hit only on that thread

TL;DR; Just press F5 when it jumps to the wrong thread.
I'm debugging a multithreaded queue processor in Visual Studio Pro 2022 Preview, I placed a breakpoint at a point where each queue item being processed would hit it. The IDE pauses because it hit the breakpoint. I press F10 (Step Over) a few times to step through the code. Then the another thread hit the breakpoint, and the IDE popped me over to that thread. I pressed F5 (Continue). The second thread continued processing, and the yellow debug-line returned to my original thread.

How to see output of a C# console program when running in VS?

I just wrote a clever program called helloworld. It's a C#/.NET 4.5 console app. Deep within the twisted nested mazes of logic there's use of Console.WriteLine().
When I'm running this at a command line, it runs and I see the output. I can do other commands and mess around a bit, and later scroll up to see the output again.
Now I'm in Visual Studio, tweaking the source ("Hi" is more efficient than "Hello") and testing by tapping F5. What happens is a console window pops up and immediately vanishes. I have no idea what the program printed. How can I see the output?
I don't want to modify my source at all. After searching for solutions, I find some who say to use Console.ReadKey() - but then it would suck to be using the program at the command line. There's no real reason the user should have to tap a key when the program has already done its work. Even if i go with this, there's the problem of the output disappearing when the console window closes after a key tap.
I don't want to use Debug.WriteLine() which does write to the output window in VS, but doesn't write ordinary output for the end user to see.
I have discovered ctrl-F5, which runs the program as if it had a final Console.ReadKey() line, but there's still the problem of when I tap any key, all the output vanishes along with the window. Three minutes later, I'm thinking "Oh wait, did it print 'Hello' or 'Helo'?" No way to check.
Seems like the Visual Studio IDE should somehow capture all that a freshly built program writes to its stdout or the Microsoft equivalent thereof, and show it in its "Output" panel, or some panel, for later scrutiny. Maybe it does do this, and I don't yet know the trick to it? Seems like this would be a common desire among millions of C# developers.

If you're working on a .NET Core console application (or .NET Framework via the .NET SDK) using Visual Studio 2019, the behaviour of leaving the console window open after the program has executed will now happen by default:
Specifically:
This should prevent the need to add Console.Read() calls to console apps to prevent the console window from closing immediately after the program has finished executing. The launched console window is also re-used for subsequent runs, so if you’re used to using ctrl+f5, you won’t have lots of console windows to close after you’ve launched your application a few times.

The reason it closes automaticly is because it's done running the program. If you want to see what it did, make it need a new command like hitting any key. The Console.ReadKey(); pauses it and waits for a User to hit a key to continue. Put that command after the commands of instruction you are doing and it will pause it until you hit any key.
Console.ReadKey(); // Pauses until you hit any key

You can also run your program pressing F10 (executes one line by one), with F11 (goes inside a function).
The other option you have is to set breakpoints in Visual Studion and run the program by pressing F5 - it will stop at the next breakpoint. And the breakpoints can have conditions - i.e. conditional breakpoints.

Some options are:
1. wrap #if DEBUG around Console.ReadKey()
2. run directly from an open terminal
3. create a Test project - but again you'll need Console.ReadKey() to stop it closing.

Call stack time machine in Visual Studio 2010

I know the title is a bit ambitious, but I am wondering if there is a way, after displaying a previous state in the call stack window (Visual Studio 2010) when debugging a C# program, to restart (like when hitting "Continue"/F5) from there.
This would be particularly useful to debug a lambda expression that generates an exception, as there is no way to move outside.
For a real OO code time machine, the historical state of all objects would need to be stored in memory, so I doubt it is feasible at this stage.
Now if the state of all objects has not changed much, then we could keep the current state and jump back in time (as a shortcut to doing the same thing with "edit and continue").

Some times, you can right click on a stack frame and choose "Unwind to here" (or very similar wording). It's not always possible, and I'm not sure what the necessary conditions are, but I'm going to make a guess as to what might prevent it:
A native code frame on the call stack in the middle
Being halted at a StackOverflowException (obviously, death to a process in any case)
Maybe lambda expressions or other things that prevent Edit-and-Continue from working (?)
Basically, anything "unusual".
Other than that, if it works, then there you go!

This is a bit kludgy but:
While viewing the previous state in the call stack window, open the disassembly window (Debug | Windows | Disassembly or CTRL+ALT+D). Now you should be able to create a breakpoint which will stop execution when you get back to that location.
If you don't care what else executes, press F5 and allow the code to run back to your new breakpoint.
Now right click on the statement you want to restart from and select Set Next Statement. Press F5 to restart from there.
If you do care about what else executes on your way back to the new breakpoint you could use Set Next Statement to set the program counter to the end of the function you are in and use Shift+F11 to step out of that function (thus not executing any of the remaining logic in that function). Repeat as needed until you get back to your new breakpoint.
Note the various dire warnings about using Set Next Statement
Edit 6/18 When I tested the above I was running Visual Studio 2010 Ultimate. I just checked Visual Studio Express C# and it does not support the Disassembly Debug Window. When I can I'll check Visual Studio 2010 Professional and update this answer again. If you have Visual Studio Ultimate then the Intellitrace suggestion by #Hans is maybe a better bet.

Debugging all events in Visual Studio 2010 without setting break points

I am trying to debug a windows form application which has a large number of events: button presses, timers, etc..
Is there a way to catch every line of code being executed by the application without setting a break point?
edit:
The program was not written by me, so I am unfamiliar with the code. I wish to step through the entire program, catching every line of code being executed. Setting break points in every event is impractical as various controls are created dynamically.

For debugging a button click without setting breakpoints:
Start the app with the debugger.
Get to the state immediately before the intended click.
Go back to the debugger and press Pause then F11 (Step Into) -- nothing will happen.
Go to the app and press the button -- the debugger should take over and drop you into the event handler.
Note: This will not work if Paint, any Mouse event, or probably some other events are handled. The debugger will drop you into those handlers any time you attempt the steps above.

If you're using the Ultimate edition of your Visual Studio 2010 you can use its new feature called IntelliTrace (previously Historical Debugger). This will allow you to do exactly what you want - be able to see all method calls and events that happened during execution of your program, and you'll be able to jump back to the event which you need.
To enable IntelliTrace, go to Tools → Options → IntelliTrace, and check the "Enable IntelliTrace" checkbox, and select one of two modes: "events only" or "events and call information", then run your application with a debugger (F5).
The difference between the two modes is that the latter uses the profiler to collect all runtime information, so you get a complete call stack, however you won't be able to use edit-and-continue features of the debugger.
You can find more in this series of articles, and of course, on MSDN.

You could also try a code coverage tool.
For example, if you have Resharper and dotCover, you can run your application (via the dotCover->Cover Application... menu item) and when the application finishes, dotCover will show you which lines of code were run in the VS IDE by highlighting them in green. Lines of code which where not run are coloured in red.
I don't know if there are other tools which do this, but it's an option.

I developed the Runtime Flow tool to solve exactly this problem - to understand a large unfamiliar .NET codebase via realtime function calls monitoring. It's similar to IntelliTrace, but places more emphasis on control flow than on debugging.

Why would you want to break on every line? This would be very onerous and time consuming. If you want to see the activity of your program as it executes, use a logging mechanism or Debug.Writeline to output information to the Immediate window.

You cannot trace lines of code, but you can use Trace.TraceInformation calls where you want to have an idea of what's executed. There's also Debug.Write. Both output will write in the output window of Visual Studio.
Another solution would be to add logging to your application, for example with log4net, but that may be overkill for your needs.

This isn't exactly what you're asking for, but in case you didn't know you can toggle an existing breakpoint on or off. In your case, you could add break points at key places throughout your code and just disable them when you don't want to debug them. That way, you'll be able to re-enable them later when you want to use them again.
Enabling/disabling is available through the Breakpoints window found under the Debug > Windows > Breakpoints menu (CTRL+D, B). You can also include "Function" and "File" columns in the window, which might help you identify which breakpoints are in the event handlers that you care about

Not really, but you can set one breakpoint and single-step (F10/F11) through the rest of the code.

Nope 'fraid not - you need to set each breakpoint yourself.
If it helps F9 is the shortcut key for assigning a breakpoint - just set a breakpoint on the start of each method and use step through (F10) / step into (F11) from there.

Why does Microsoft Visual C# 2008 Express Edition debugger randomly exit?

I am writing a multi-threaded Windows application in Microsoft Visual C# 2008 Express Edition. Recently, the debugger has been acting strangely.
While I am Stepping Over lines of code using the F10, sometimes it will interpret my Step Over (F10) command just like a Continue command (F5) and then the program will resume running and the debugging session will be done.
Does anyone know why this happening? In what circumstances can the Step Over command result in the debugger stopping?
It's not a problem with the code being debugged: it doesn't just happen on particular lines of code. It happens on a random line that is different each time I run the debugger.
It's not a problem with my keyboard: the same thing happens when I just click Step Over in the Debug toolbar.
It may be a problem with the other threads in my program. Maybe one of them is randomly doing something that has a side effect of interrupting the debugger. Is that possible?
Thanks in advance!

You ought to take a look at this KB article and consider its matching hotfix.
EDIT: the hotfix does solve these kind of debugging problems. Unfortunately, the source code changes for the hotfix didn't make it back into the main branch and VS2010 shipped with the exact same problems. This got corrected again by its Service Pack 1.

I've seen this a few times. It generally happens when there's a context switch to another thread. So you might be stepping through thread with ID 11, you hit F10, and there's a pre-emptive context switch so now you're running on thread ID 12 and so Visual Studio merrily allows the code to continue.
There are some good debugging tips here:
Tip: Break only when a specific thread calls a method: To set a per-thread breakpoint, you need to uniquely identify a particular thread that you have given a name with its Name property. You can set a conditional breakpoint for a thread by creating a conditional expression such as "ThreadToStopOn" == Thread.CurrentThread.Name .
You can manually change the name of a thread in the Watch window by watching variable "myThread" and entering a Name value for it in the value window. If you don't have a current thread variable to work with, you can use Thread.CurrentThread.Name to set the current thread's name. There is also a private integer variable in the Thread class, DONT_USE_InternalThread, this is unique to each thread. You can use the Threads window to get to the thread you want to stop on, and in the Watch window, enter Thread.CurrentThread.DONT_USE_InternalThread to see the value of it so you can create the right conditional breakpoint expression.
EDIT: There are also some good tips here. I found this by googling for 'visual studio prevent thread switch while debugging'.

I find using a logfile is very handy when dealing with multiple threads.
Debugging threads is like the Huysenberg principle - observe too closely and you'll change the outcome !

Try this http://support.microsoft.com/kb/957912. Worked for me.