[c#] Attempted to read or write protected memory. This is often an indication that other memory is corrupt

I'm hoping someone can enlighten me as to what could possibly be causing this error:

Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

I cannot really post code because this error seems to get thrown in any random area of the application. The application will run anywhere from 12-48 hours before throwing the error. Sometimes it will stop in a seemingly random spot and throw the above error, other times the entire application stops and I get a screen with an error that says something along the lines of "There was a fatal error in... This may be a bug in the CLR or..." something about PInvoke or other non relevant info. When this happens all threads show terminated and there is no debugging information available.

In a nutshell this is what the application does:

Its a multi-threaded server application written in entirely in C#. Clients connect to the server via socket. The server runs a virtual "environment" for the clients where they can interact with each other and the environment. It consumes quite a bit of memory but I do not see it leaking. It typically consumes about 1.5GB. I dont think its leaking because the memory usage stays relatively constant the entire time the application is running. Its constantly running code to maintain the environment even if the clients are not doing anything. It uses no 3rd party software or other APIs. The only outside resources this application uses is socket connections and SQL database connections. Its running on a 64bit server. I have tried debugging this in VS2008 & VS2010 using .net 2.0, 3.5, and 4.0 and on multiple servers and the problem still eventually occurs.

I've tried turning off compiler optimizations and several microsoft hot-fixes. Nothing seems to make this issue go away. It would be appreciated if anyone knows any possible causes, or some kind of way to identify whats causing the problem.

My answer very much depends on your scenario but we had an issue trying to upgrade a .NET application for a client which was > 10 years old so they could make it work on Windows 8.1. @alhazen's answer was kind of in the correct ballpark for me. The application was relying on a third-party DLL the client didn't want to pay to update (Pegasus/Accusoft ImagXpress). We re-targeted the application for .NET 4.5 but each time the following line executed we received the AccessViolationException was unhandled message:

UnlockPICImagXpress.PS_Unlock (1908228217,373714400,1341834561,28447);

To fix it, we had to add the following post-build event to the project:

call "$(DevEnvDir)..\tools\vsvars32.bat"
"C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\bin\amd64\editbin.exe" /NXCOMPAT:NO "$(TargetPath)"

This explicitly specifies the executable as incompatible with Data Execution Prevention. For more details see here.

This may not be the best answer for the above question, but the problem of mine was invalid dispose syntax and usage of lock(this) for a buffer object. It turned out the object was getting disposed from another thread because of "using" syntax. And the processing lock() was on a loose type.

// wrong lock syntax
lock(this) {
    // modify buffer object
}

I changed the locks to

private static readonly object _lockObject = new object();

lock(_lockObject) {
    // modify buffer object
}

And used suggested C# disposing syntax and the problem gone.

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing)
    {
        if (disposed)
            return;

        if (disposing)
        {
            // Free any managed objects here
            buffer?.Free();
        }

        disposed = true;
    }

This issue is almost invariably a simple one. The code is bad. It's rarely the tools, just from a statistical analysis. Untold millions of people are using Visual Studio every day and maybe a few are using your code - which bit of code is getting the better testing? I guarantee that, if this were a problem with VS, we would probably already have found it.

What the statement means is that, when you try to access memory that isn't yours, it's usually because you're doing it with a corrupted pointer, that came from somewhere else. That's why it's stating the indication.

With memory corruption, the catching of the error is rarely near the root cause of the error. And the effects are exactly what you describe, seemingly random. You'll just have to look at the usual culprits, things like:

• uninitialised pointers or other values.
• writing more to a buffer than its size.
• resources shared by threads that aren't protected by mutexes.

Working backwards from a problem like this to find the root cause is incredibly difficult given that so much could have happened between the creation of the problem and the detection of the problem.

I mostly find it's easier to have a look at what is corrupt (say, a specific pointer) and then do manual static analysis of the code to see what could have corrupted it, checking for the usual culprits as shown above. However, even this won't catch long chains of problems.

I'm not familiar enough with VS to know but you may also want to look into the possibility of using a memory tracking tool (like valgrind for Linux) to see if it can spot any obvious issues.

I faced the same issue. My code was a .NET dll (AutoCAD extension) running inside AutoCAD 2012. I am also using Oracle.DataAccess and my code was throwing the same exception during ExecuteNonQuery(). I luckily solved this problem by changing the .net version of the ODP I was using (that is, 2.x of Oracle.DataAccess)

I also faced this issue with Visual Studio(VS) 2010. More interestingly, I had several projects in my solution (Console application, WPF application, Windows Forms application) but it was failing only when, I was setting the "Console Application" type of project as start up project of the solution(Even for those which had literally no code or any additional assemblies referred apart from the default ones which come with project template itself).

Following change finally helped me nail down the issue: Go to project properties of the console application project (Alternatively, select project file in solution explorer and press Alt + Enter key combination) -> Go to Debug tab -> Scroll to Enable Debuggers section in right pane -> Check the Enable unmanaged code debugging check box as shown in the snapshot below -> Click Floppy button in the toolbar to save project properties. Root cause of why it happened is still not known to me. Only thing I observed was that there were lot of windows updates which had got installed on my machine the previous night which mostly constituted of office updates and OS updates (More than a dozen KB articles).

Update: VS 2017 onward the setting name has changed as shown in the screenshot below:

I got the same error in a project I was working with in VB.NET. Checking the "Enable application framework" on the properties page solved it for me.

i had this problem too . i was running different solutions at the same time using visual studio , when closing other solutions and running just the target solution , it worked fine without that error .

Try to run this command

netsh winsock reset

Source: https://stackoverflow.com/a/20492181/1057791

The problem may be due to mixed build platforms DLLs in the project. i.e You build your project to Any CPU but have some DLLs in the project already built for x86 platform. These will cause random crashes because of different memory mapping of 32bit and 64bit architecture. If all the DLLs are built for one platform the problem can be solved.

I have just faced this issue in VS 2013 .NET 4.5 with a MapInfo DLL. Turns out, the problem was that I changed the Platform for Build from x86 to Any CPU and that was enough to trigger this error. Changing it back to x86 did the trick. Might help someone.

In my case the FTDI utility FT Prog was throwing the error as it scanned for USB devices. Unplugging my Bluetooth headphones from the PC fixed the issue.

I got this error message on lambda expression that was using Linq to filter a collection of objects. When I inspected the collection I noticed that its members weren't populated - in the Locals window, expanding them just showed "...". Ultimately the problem was in the repository method that initially populated the collection - Dapper was trying to automatically map a property of a nested object. I fixed the Dapper query to handle the multi-mapping and that fixed the memory error.

I had this problem recently when I changed the development server for a project. I was getting this error on the line of code where I declared a new OracleConnection variable.

After trying many things, including installing hotfixes, I tried changing the references Oracle.DataAccess and System.Data.OracleClient in the project and it worked!

When a project is moved to a new machine, I suggest you renew all the references added in that project.

In my case I had to reference a C/C++ library using P/Invoke, but I had to ensure that the memory was allocated for the output array first using fixed:

[DllImport("my_c_func_lib.dll", CharSet = CharSet.Ansi)]
public static extern unsafe int my_c_func(double input1, double input2, double pinput3, double *outData);

    public unsafe double[] GetMyUnmanagedCodeValue(double input1, double input2, double input3)
    {
        double[] outData = new double[24];

        fixed (double* returnValue = outData)
        {
            my_c_func(input1, input2, pinput3, returnValue);
        }

        return outData;
    }

For details please see: https://www.c-sharpcorner.com/article/pointers-in-C-Sharp/

It could be hardware. It could be something complicated...but I'd take a stab at suggesting that somewhere your threading code is not protecting some collection (such as a dictionary) with an appropriate lock.

What OS and service pack are you running?

Got this error randomly in VS1017, when trying to build a project that was building perfectly fine the day before. Restarting the PC fixed the issue worked (I also ran the following command beforehand, not sure if it's required: netsh winsock reset)

Verifiable code should not be able to corrupt memory, so there's something unsafe going on. Are you using any unsafe code anywhere, such as in buffer processing? Also, the stuff about PInvoke may not be irrelevant, as PInvoke involves a transition to unmanaged code and associated marshaling.

My best recommendation is to attach to a crashed instance and use WinDBG and SOS to dig deeper into what's happening at the time of the crash. This is not for the faint of heart, but at this point you may need to break out more powerful tools to determine what, exactly, is going wrong.

This happened to me when I was debugging my C# WinForms application in Visual Studio. My application makes calls to Win32 stuff via DllImport, e.g.

[DllImport("Secur32.dll", SetLastError = false)]
private static extern uint LsaEnumerateLogonSessions(out UInt64 LogonSessionCount, out IntPtr LogonSessionList);

Running Visual Studio "as Administrator" solved the problem for me.

in my case the file was open and therefore locked.

I was getting it when trying to load an Excel file using LinqToExcel that was also opened in Excel.

this is all I deeded

    var maps = from f in book.Worksheet<NavMapping>()
                select f;
    try {
        foreach (var m in maps)
            if (!string.IsNullOrEmpty(m.SSS_ID) && _mappings.ContainsKey(m.SSS_ID))
                _mappings.Add(m.SSS_ID, m.CDS_ID);
    } catch (AccessViolationException ex) {
        _logger.Error("mapping file error. most likely this file is locked or open. " + ex);
    }

I've ran into, and found a resolution to this exception today. It was occurring when I was trying to debug a unit test (NUnit) that called a virtual method on an abstract class.

The issue appears to be with the .NET 4.5.1 install.

I have downloaded .NET 4.5.2 and installed (my projects still reference .NET 4.5.1) and the issue is resolved.

Source of solution:

https://connect.microsoft.com/VisualStudio/feedback/details/819552/visual-studio-debugger-throws-accessviolationexception

I got this error when using pinvoke on a method that takes a reference to a StringBuilder. I had used the default constructor which apparently only allocates 16 bytes. Windows tried to put more than 16 bytes in the buffer and caused a buffer overrun.

Instead of

StringBuilder windowText = new StringBuilder(); // Probable overflow of default capacity (16)

Use a larger capacity:

StringBuilder windowText = new StringBuilder(3000);

Ok, this could be pretty useless and simply anecdotal, but...

This exception was thrown consistently by some Twain32 libraries we were using in my project, but would only happen in my machine.

I tried lots of suggested solutions all over the internet, to no avail... Until I unplugged my cellphone (it was connected through the USB).

And it worked.

Turns out the Twain32 libraries were trying to list my phone as a Twain compatible device, and something it did in that process caused that exception.

Go figure...

I had the same error message:

System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

In my case, the error went away after clean and re-build the solution.

Did you try turning off DEP (Data Execution Prevention) for your application ?

This error should not happen in the managed code. This might solve the issue:

Go to Visual Studio Debugger to bypass this exception:

Tools menu ->Options -> Debugging -> General -> Uncheck this option "Suppress JIT optimization on module load"

Hope it will help.

In some cases, this might happen when:

obj = new obj();
...
obj.Dispose();  // <-----------------    Incorrect disposal causes it
obj.abc...