An attempt was made to load a program with an incorrect format

I want my C# application to conditionally run a native method. Deciding at run time whether to run either the x86 or the x64 version of the dll.

This question explains how to choose 32 bit or 64 bit at compile time, but that does not help. I want to make the decision at runtime.

I’m currently doing the following:

But when I try to call the x86 method I get the error:

Any idea how I can conditionally load either the x86 or the x64 version of the dll?

(Note: dbghelpx86.dll is the x86 version of dbghelp.dll that I renamed)

1 Answer 1

Your program will be either 32-bit or 64-bit. It is not possible to execute 32-bit code in an 64-bit program, and it is not possible to execute 64-bit code in a 32-bit program. You will get a run-time exception if you try! Thus, you cannot have 1 program which executes both x86 and x64 code. You have 3 options depending on what you would like to do.

Use «Any CPU», and then your program can run as 32-bit on a 32-bit platform and 64-bit on a 64-bit platform. In that case, you can use this code to determine which DLL to use and you would only need 1 assembly to be able to handle both 32-bit and 64-bit platforms and it will use the correct dll:

If you want to use «preprocessor» conditions to do this, then you would compile 2 different assemblies. You would compile a 32-bit assembly to be run on 32-bit platforms which uses the 32-bit DLL, and you would compile a separate 64-bit assembly to run in 64-bit platforms.

Use IPC(Inter-process-communications). You would have 1 64-bit program which «connects» to a 32-bit program. The 64-bit program can run the 64-bit DLL function, but when you need to run the 32-bit DLL function, you would have to send a message to the 32-bit program with the information needed to run it, and then the 32-bit program could send a response with any information that you want back.

Could not load file or assembly ‘xxx’ or one of its dependencies. An attempt was made to load a program with an incorrect format

I just checked out a revision from Subversion to a new folder. Opened the solution and I get this when run:

Could not load file or assembly ‘xxxx’ or one of its dependencies. An attempt was made to load a program with an incorrect format.

This is the same code I had checked in a while ago. Why now is it doing this? I now also see a Debug x86 instead of just Debug in that xxx project’s bin folder. What is Debug x86 and why don’t I just have Debug only like I used to in the bin folder?

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Sounds like one part of the project is being built for x86-only while the rest is being built for any CPU/x64. This bit me, too. Are you running an x64 (or uh. IA64)?

Check the project properties and make sure everything is being built for «Any CPU». f you’re in Visual Studio, you can check for everything by going to the «x86» or «Any CPU» menu (next to the «Debug»/»Release» menu) on the toolbar at the top of the screen and clicking «Configuration Manager. «

If you get this error while running the site in IIS 7+ on 64bit servers, you may have assemblies that are 32bit and your application pool will have the option «Enable 32-Bit Applications» set to False; Set this to true and restart the site to get it working.

They ship five BusinessObjects*.dll files, but all of them are 64-bit.

To get my webpage to load, I needed to click on Tools\Options, then change this setting in VS2013:

inetmgr then come to Application pool->Advanced setting of your pool-> will have the option «Enable 32-Bit Applications» set to true; and restart IIS. check again.!

Make sure you verify your setting for «Prefer 32-bit». In my case Visual Studio 2012 had this setting checked by default. Trying to use anything from an external DLL failed until I unchecked «Prefer 32-bit».

The BadImageFormatException on an application running on IIS (not running from VS, since visual studio fixes the problem by using the build for «Any CPU») can be caused by the following:

The site is one a server that is x64 and the Application Pool’s default setting for Enable 32-Bit Applications was False. and you have 32-bit assemblies

On the level of Visual Studio, the fix is:

It’s definitely an issue with some of the projects being built for x86 compatibility instead of any CPU. If I had to guess I would say that some of the references between your projects are probably referencing the dll’s in some of the bin\debug folders instead of being project references.

When a project is compiled for x86 instead of ‘Any CPU’ the dll’s go into the bin\x86\debug folder instead of bin\debug (which is probably where your references are looking).

But in any case, you should be using project references between your projects.

if while In visual studio with IIS express working and when published failed try this:

IIS 7.5 Fixing An attempt was made to load a program with an incorrect format problem?

I have a unusual problem throwing an exception «An attempt was made to load a program with an incorrect format» error? I have two identical websites on the same IIS server and my build configuration works for one of them but not the other.

My C# MVC 2 web app can deployed to two websites that reside on the same IIS 7.5 webserver (x64). One is the live site (deployed using Release configuration), the second is the beta site (deployed using a new Beta configuration created just for this project). The codebase for both projects is the same. They have different build configurations, but the settings inside the configurations are identical.

Deploying the release configuration to Default Website/my_app works perfectly.

Deploying the beta configuration to Beta/my_app deploys, but when I load the site (any page) I get the incorrect format exception.

I cannot understand why deploying with the exact same config settings would work for one website but not another (on the same webserver). My server + dev machines are 64 bit, and both websites have the same app pool settings (.NET 4, integrated).

How can I find/fix this problem? Preferably without having to have different config settings for each site. And preferably without having to change the release config since that is working and I don’t want to risk changing it.

The two websites are:

The configuration manager for release has these settings:

The configuration manager for beta has the exact same settings:

The exception is:

I’ve seen that there are multiple questions on SO asking about «An attempt was made to load a program with an incorrect format» but I do not believe this to be a duplicate. This is a unique situation with the config working fine on one site but not on another using the same config settings and the same webserver for both.

I get a «An attempt was made to load a program with an incorrect format» error on a SQL Server replication project

The exact error is as follows

Could not load file or assembly ‘Microsoft.SqlServer.Replication, Version=9.0.242.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91’ or one of its dependencies. An attempt was made to load a program with an incorrect format.

I’ve recently started working on this project again after a two month move to another project. It worked perfectly before, and I’ve double checked all the references.

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The answer by baldy below is correct, but you may also need to enable 32-bit applications in your AppPool.

Whilst setting up an application to run on my local machine (running Vista 64bit) I encountered this error:

Could not load file or assembly ChilkatDotNet2 or one of its dependencies. An attempt was made to load a program with an incorrect format.

Obviously, the application uses ChilKat components, but it would seem that the version we are using, is only the 32bit version.

To resolve this error, I set my app pool in IIS to allow 32bit applications. Open up IIS Manager, right click on the app pool, and select Advanced Settings (See below)

Then set «Enable 32-bit Applications» to True.

I’ve found the solution. I’ve recently upgraded my machine to Windows 2008 Server 64-bit. The SqlServer.Replication namespace was written for 32-bit platforms. All I needed to do to get it running again was to set the Target Platform in the Project Build Properties to X86.

We recently had the issue when trying to run the code from Visual Studio. In that case you need to do
TOOLS > OPTIONS > Projects and Solutions > WEB PROJECTS and check the «Use the 64 bit version of IIS Express for web sites and projects».

For those who get this error in an ASP.NET MVC 3 project, within Visual Studio itself:

In an ASP.NET MVC 3 app I’m working on, I tried adding a reference to Microsoft.SqlServer.BatchParser to a project to resolve a problem where it was missing on a deployment server. (Our app uses SMO; the correct fix was to install SQL Server Native Client and a couple other things on the deployment server.)

Even after I removed the reference to BatchParser, I kept getting the «An attempt was made. » error, referencing the BatchParser DLL, on every ASP.NET MVC 3 page I opened, and that error was followed by dozens of page parsing errors.

If this happens to you, do a file search and see if the DLL is still in one of your project’s \bin folders. Even if you do a rebuild, Visual Studio doesn’t necessarily clear out everything in all your \bin folders. When I deleted the DLL from the bin and built again, the error went away.

I am building a 64bit only web application ( AssemblyA ) and referencing another application I have built which is also 64bit only ( AssemblyB ).

ASPNETCOMPILER Could not load file or assembly ‘AssemblyB’ or one of its dependencies. An attempt was made to load a program with an incorrect format.

I have used the aspnet_compiler.exe command line tool with the errorstack option enabled and got the following stack trace:

[BadImageFormatException]: Could not load file or assembly ‘AssemblyB’ or one of its dependencies. An attempt was made to load a program with an incorrect format.

at System.Reflection.RuntimeAssembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntro spection, Boolean suppressSecurityChecks)

at System.Reflection.RuntimeAssembly.nLoad(AssemblyName fileName, String code Base, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& s tackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntros pection, Boolean suppressSecurityChecks)

at System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, RuntimeAssembly reqAssembly, StackCrawlMark &stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks)

at System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark &stackMark, IntPtr pPrivHostBinder, Boolean forIntrospection)

at System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark &stackMark, Boolean forIntrospection)

at System.Reflection.Assembly.Load(String assemblyString)

at System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective)

[ConfigurationErrorsException]: Could not load file or assembly ‘AssemblyB’ or one of its dependencies. An attempt was made to load a program with an incorrect format.

at System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective)

at System.Web.Configuration.CompilationSection.LoadAllAssembliesFromAppDomain BinDirectory()

at System.Web.Configuration.CompilationSection.LoadAssembly(AssemblyInfo ai)

at System.Web.Compilation.BuildManager.GetReferencedAssemblies(CompilationSection compConfig)

at System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStar tInitListPath, Boolean& isRefAssemblyLoaded)

at System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, Host ingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException)

I have looked at the following related questions and none answer this question. Most relate to IIS configuration, which is not the case as this is a compilation error, or have the solution as setting the project to allow 32bit platform target, which is not suitable for my case:

I am at a loss as to where to go from here. To reiterate, I do not want to set either of my projects to 32bit and this isn’t a problem with IIS config as this is a compilation error.

I have also tried it on several different machines and on brand new applications with the same result.