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Unable to load libraries (.dll) in a C# Website Application

We have a .Net application that successfully "load" .dll libraries from a specific folder in Windows Operative System. The .Net framework we have been using so far is 4.6. All the .dll libraries that the application loads were compiled in x86. The following code is an excerpt of how we are loading the libraries and getting their types:
1. try{
2. AssemblyFileDescriptor assemblyFile = new AssemblyFileDescriptor(assemblyPath);
3. var assm = Assembly.LoadFrom(assemblyPath);
4. var types = assm.GetExportedTypes();
5. ...
6. }catch (Exception e) {
7. ...}
The libraries in a specific folder, let's say
C:\Program Files (x86)\FOLDER
, are loading to the variable assm without any exception. The problem occurs when we migrated our .Net "stand alone" application to a website application with a Web.config file. In the website application, the load function fails when getting the types. Then the 4th line throws the exception. We have been using the ISS Express.
We have already tried:
Using a different Load function such as "UnsafeLoadFrom".
Re-compiling all the .dll libraries in x86 and x64.
Setting up different configurations for the Web.Config file such as including <trust level="Full" /> or <loadFromRemoteSources enabled="true" />.
Debugging the loading function of each library. Some of them can load successfully, but there are others that throw a Loading Exception.
Setting in the ISS Express "True" the variable "Enable 32-bit applications".
The specific error states "System.Reflection.ReflectionTypeLoadException":
Any idea of how tackling this issue? Let me know if you need further information.

I'm guessing you're running this under IIS, and IIS usually runs as a different user than you (usually IUSR), and usually has limited permissions. Converting a standalone program to an ASP.NET program changes a lot of things in subtle ways. I'd check to make sure you aren't running into a file-permission issue because IIS is a restricted user.
Also, as others pointed out, you should probably provide the exception details (at least its typename and message) so people don't have to guess at it.

According to the answers of this question and several loading experiments that we had been performing in the website application. We observed a pattern related to the framework version that we used for compiling the DLLs and the ReflectionTypeLoadException. Some DLLs were compiled with framework 3.5, this version does not allow loading libraries in ISS with .Net CLR2. Then, we must rebuild all the DLLs and their dependencies with a higher version of the framework (.Net v4.0). Finally, we re-loaded the updated DLLs in ISS express with .NET CLR4. The DLLs were loaded without any exception.

Windows Service: The module was expected to contain an assembly manifest

I've got a C# program that was built as a Windows service. I tested this last week and it worked fine, but today I'm getting an error.
When I try to install using installutil.exe, I get the error:
Could not load file or assembly [file name] or one of its dependencies. The module was expected to contain an assembly manifest.
Rebuilding the project had no effect. I also noticed in task manager that the service is still listed and running. On the chance that might be interfering with the installation, I tried uninstalling via installutil, but got the same error message back again.
I've seen many other questions related to this error, but most of them have either no answer, or a very specific answer related to their unique situation. Has anybody had this happen, and how did you fix it? Any ideas are appreciated.
Update:
I successfully uninstalled the service using the "sc delete" command via command prompt, but I'm still getting the same error from installutil on trying to reinstall.
Update 2:
Just for the sake of trying something, I deleted the bin folder from the project, reopened the solution, and did a clean and build. It still won't install, but now I've got a different message:
This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded.
Question:
What would cause there to be a mismatch in runtimes? As far as I know, I've only used .NET Framework 4.5 and haven't deviated. Is there a value I should be looking at / changing to fix that?
Update 3:
Here's what I've tried so far:
One answer suggested the version of installutil being used matters. I'd been running v2.0.50727, but there's also a v4.0.30319 I hadn't thought to try. Running this resulted in:
An attempt was made to load a program with an incorrect format...
I'd be willing to work on that error instead, if it would solve the problem. However, I'm compelled to think that's not the problem since I'd been successfully running v2.0.etc just before the first error popped up.
Inside App.config, there's a line "supported Runtime version=v4.0". I switched this to 4.5, but it had no effect good or bad.
I tried switching the target framework (under project properties) down to 4.0, but this cause an error with:
Some NuGet packages were installed using a target framework different from the current target framework, etc...
This was referring to the EntityFramework, and I'd rather not start messing with NuGet again unless it's the only way (last time it was a nightmare).
I tried installing the service on the target server (the machine it will eventually be deployed to) and got the same error. This leads me to think it's a problem with the project / solution and not the pc.

Looks like a assembly loading problem. Use the Fuslogvw.exe utility. Start it from the Visual Studio Command Prompt. Click the Settings button and click the "Log binding failures to disk" radio button. Switch back to VS and start the program and wait for the exception to occur. Back to Fuslogvw, click the Refresh button and double-click the added entry. It will show you the file it found.
One another possibility is to trying to load a .NET 4 assembly with an EXE that asked for CLR version 2. That requires an app.exe.config file that forces CLR 4 to be used.

C# Released program , .exe and dll, when hit start, works on my computer but not others

So basically I coded something and when I press start, it uses content from dlls etc..
And when I do it everything works fine I got all the .dlls in the same folder as the .exe,
but on someone else's computer it just wont work, it crashes, boom.
Even though he has everything 100% like me
I don't know what to do to find what causes this, any way to know?
private void nsButtonAutoStart_Click(object sender, EventArgs e)
{
secondThread = new Thread( () => Start(dsflfsdl, sgdsgd, sggdsg, etc));
secondThread.Start();
}
What it does is :
if (!Directory.Exists(user))
Directory.CreateDirectory(user);
than create more folders with a given name etc.. well I won't describe everything, just need to know how to spot what's wrong.

There are several exceptions that can be thrown from this, so I'll go over causes of the most likely culprits...
Framework: this can be the case when the .NET Framework is not installed, or the right version isn't installed. Note that the System.___ Dlls are ususally included in the GAC, but can sometimes be missing. Install a GAC Browser tool and make sure everything you reference in your project is not only installed, but also show up properly in the GAC.
Permissions: It's possible that since the program is rexognized as coming from somewhere else and lacks publisher signing, it doesn't have filesystem permissions, and is thus crashing for even trying to look at files. This can be resolved by trying to have the other computer Run as Administrator in Windows. This can also cause DLL Not Found exceptions because of being unable to reach into the running directory for required Dlls.
How to find the exception: If the client sees a "program has stopped working" window, there'll often be the option to see "more details," in which one of the lines of "More Data X" will be the actual exception type.
Missing Method Exception: this can happen if it can't find a method. This can happen if you're "providing" DLLs that are also present on the GAC (say, System or mscorlib). Becuase Assembly Resolution checks the GAC first, it will use the GAC version if it's present, even if you've provided a copy. This can cause issues if you don't specify the requirement of a specific version, becuase it could hook into a .NET 4.0 assembly where it should be grabbing a 4.5 one. Make sure the right version of .NET is installed, and try making your project Require Sepcific Version: True for all references

I found the problem, basically it was the .dll that they had , it was the good one but it lacked some data in it, it was 300 kb instead of 454 kb

DLL not found in distributed application

I've written a pretty simple Windows Form Application that calls an unmanaged DLL to perform most of the actual calculations done by the program. The program runs fine in Debug and Release modes. It also installs correctly and runs on the development computer.
The problem arises when I attempt to install it on target computer (running the same operating system: 64bit Windows 7). Despite the DLL being in the same directory as the .exe file, I'm getting a "DLL Not Found Exception". I'm getting this exception when I attempt both OneClick publishing as well as when I use a .msi installation file. The error will even cite the location of the file while stating the file could not be found.
Is one of my installer settings incorrect? Am I not including the DLL or a reference in the appropriate place? Any help or advice would be appreciated.
Thanks.

The DLL you deployed may have additional dependencies that you haven't deployed. If those dependencies aren't there then you'll generally get this type of error.
UPDATE:
The "D" in MSVCR100D means that it's the debug version of the library. That most likely isn't on the target system and licensing prevents you from deploying it.
You need to do a full recompile under Release mode. Once that is done your DLL should target MSVCR100 (note the lack of "D") instead. If not, then you probably have a debug build of that assembly. Locate a release version and link to that.

If you are invoking the unmanaged code by calling CreateObject then make sure that you have registered the unmanaged DLL on target computer as well.

In a post about a similar 'dll not found' error at Microsoft: http://support.microsoft.com/kb/319114 you can learn how to fix this problem based on the fact that it might happen due to: 1) Missing or corrupt dll file (also here) 2) The registration path which is calling that that dll is probably wrong/missing/damaged somehow. Otherwise you might want to verify that new virus/malware is around...

Why can't my .NET CF application find a DLL In the same directory as the executable?

I have a .NET CF 1.1 application that has been running perfectly fine for years. Occasionally, I get a help desk ticket with the following error message (generic):
Method not found:
MethodName
AssemblyNamespace.Class
The DLL is there, and it's the same version as my other devices. What could change that would make it not find the method. Does this error imply that the assembly was loaded, or did it break before that even happened?
Does it matter how I added the reference in Visual Studio (2003, btw)? I have Copy Local set to true, and therefore I made the assumption that it needs to be in the same directory as my executable.
Any help you can offer is appreciated. Thanks.
EDIT: I believe this DLL is also in the windows directory of the device, possibly a different version. It contains a lot of hardware specific functions (i.e. backlight, keyboard state, etc.)

No it does not matter how you add the reference in Visual studio 2003. (100% sure)
Now for the not so sure : I think that someone else has the same assembly in the GAC of the phone. So the GAC assembly gets called rather than the one you deployed and that version of the assembly lacks the requested function.

Depends on how you reference the file in your code. You could be relying on the current working directory which depending on how the app is launched or what they do after, it might not be what you expect it to be.

Sometimes .NetCf throws this exception when the device is running out of memory, instead of the expected "Out of Memory" exception. I have observed this behaviour more often when loading native dlls using P/Invoke than loading pure netcf dlls.