Reputation: 27021

Error message 'Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.'

I have developed an application using Entity Framework, SQL Server 2000, Visual Studio 2008 and Enterprise Library.

It works absolutely fine locally, but when I deploy the project to our test environment, I am getting the following error:

Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information

Stack trace: at System.Reflection.Module._GetTypesInternal(StackCrawlMark& stackMark)

at System.Reflection.Assembly.GetTypes()

at System.Data.Metadata.Edm.ObjectItemCollection.AssemblyCacheEntry.LoadTypesFromAssembly(LoadingContext context)

at System.Data.Metadata.Edm.ObjectItemCollection.AssemblyCacheEntry.InternalLoadAssemblyFromCache(LoadingContext context)

at System.Data.Metadata.Edm.ObjectItemCollection.AssemblyCacheEntry.LoadAssemblyFromCache(Assembly assembly, Boolean loadReferencedAssemblies, Dictionary2 knownAssemblies, Dictionary2& typesInLoading, List`1& errors)

at System.Data.Metadata.Edm.ObjectItemCollection.LoadAssemblyFromCache(ObjectItemCollection objectItemCollection, Assembly assembly, Boolean loadReferencedAssemblies)

at System.Data.Metadata.Edm.ObjectItemCollection.LoadAssemblyForType(Type type)

at System.Data.Metadata.Edm.MetadataWorkspace.LoadAssemblyForType(Type type, Assembly callingAssembly)

at System.Data.Objects.ObjectContext.CreateQuery[T](String queryString, ObjectParameter[] parameters)

Entity Framework seems to have issue, any clue how to fix it?

Upvotes: 422

Answers (30)

Jeremy Thompson

Reputation: 65712

I hit this today upgrading a solution from .Net 4 to 8.

When I load a ABC.DLL

Type[] types = Assembly.LoadFile(pluginPath).GetTypes();

It gives me the error:

It can't find the file or assembly XYZ.DLL which is a project reference in ABC.

The code that loads the Assembly is in a Library I can't easily change. I tried everything to resolve the error.

Confirmed the XYZ.DLL lives in the same folder as ABC.DLL.

I tried Fusion Viewer and there was nothing for today:

I even tried Process Monitor and there's no evidence of the DLL being loaded.

So that gave me an idea, load the XYZ Dependency directly to get it in the system (somehow make it recognised):

AssemblyLoadContext.Default.LoadFromAssemblyPath(pluginDependencyPath);

Then load the main plugin

Assembly pluginAssembly = 
AssemblyLoadContext.Default.LoadFromAssemblyPath(pluginPath);

Retrieve types

Type[] types = pluginAssembly.GetTypes();

And then when the old code runs and loads the .Net 8.0 DLL, it can find it:

Type[] types = Assembly.LoadFile(pluginPath).GetTypes();

I'm not sure why pre-loading the DLL with the AssemblyLoadContext fixes it, but it works!

Upvotes: 0

Timofeus

Reputation: 309

In my case there was a problem with netstandard2.0 lib referenced by my net4.8 windows service project. Curiously, it worked with the application, but throwed an error during installation with installutil.exe.

Upvotes: 0

Saibamen

Reputation: 658

Also check if you don't have <Private>True</Private> for not loaded assemblies in your .csproj files

Upvotes: 0

neizan

Reputation: 2321

If you're getting this error when referencing a .dll in PowerShell, and your .dll is .NET 5 (.NET Core, too?), then you should ensure you're executing the PowerShell script in PowerShell 6+ instead of Windows PowerShell 5.1 (or earlier version). That helped me in a specific scenario.

Upvotes: 0

Kenny Eliasson

Reputation: 2052

One solution that worked for me was to delete the bin/ and obj/ folders and rebuild the solution.

Update:

Or you can try to right-click the Solution node in the "Solution Explorer" and click "Clean Solution", then click "Rebuild Solution" (thanks Emre Guldogan)

Upvotes: 80

Rupesh Kumar Tiwari

Reputation: 967

In My case I had one nuget package that was installed in my project however package folder was never checked in to TFS therefore, in build machine that nuget package bin files were missing. And hence in production I was getting this error. I had to compare the bin folder over production vs my local then I found which dlls are missing and I found that those were belonging to one nuget package.

Upvotes: 0

Obi-Wan Kenobi

Reputation: 51

I had this issue while referencing a nuget package and later on using the remove option to delete it from my project. I had to clear the bin folder after battling with the issue for hours. To avoid this its advisable to use nuget to uninstall unwanted packages rather than the usual delete

Upvotes: 1

user1760527

Reputation: 1164

It happened for me also. I solved the problem as follows: Right click Solution, Manage NuGet Packages for Solution... Consolidate packages and upgraded the packages to be in the same version.

Upvotes: 1

Code_Worm

Reputation: 4470

I encountered this issue with entity framework when typing migration commands in Nuget console.

the problem showed up when I moved my OAuthAuthorizationServerProvider codes from my application into a class library project which contained core data access logic as well as my DBContext class.

I check all my DLLs referenced by the class library project. and for all of them (except .net system DLLs) CopyToLocal was true I was completely confused.

I knew that there was something wrong with DLLs themselves not my codes. I checked them again and I noticed that when I moved my ApplicationOauthProvider class into a class library project the ApplicationOauthProvider inherits from OAuthAuthorizationServerProvider class which is located in Microsoft.Owin.Security.OAuth assembly, I checked it's package version and suddenly noticed that the version of package that I used for the class library project (not my application project) is very old 2.1, but on my application the latest version was installed (3.0.1) so I upgraded version of the Microsoft.Owin.Security.OAuth package from Nuget fo my class library project and problem got away

In short after checking CopyToLocal property of your DLLs check their versions too and update the old ones to letest version

Upvotes: 0

Dev

Reputation: 1541

The solution was to check the LoaderException: In my case, some of the DLL files were missing.

Upvotes: 20

jkindwall

Reputation: 3906

In case none of the other answers help you:

When I had this problem, it turned out my Windows service was built for an x64 platform, and I was inadvertently running the 32-bit version of InstallUtil.exe. So make sure you're using the right version of InstallUtil for the platform you built for.

Upvotes: 2

user2814851

Reputation: 93

My issue has been resolved after I deleted the redundant assembly files from the bin folder.

Upvotes: 3

jayson.centeno

Reputation: 835

I got this problem when I installed a NuGet package on one of the projects and forgot to update the other project.

I solved this by just making both projects having the same reference assembly.

Upvotes: 1

Valamas

Reputation: 24759

I was updating a website via FTP. I assume the website was in use and when trying to update the bin folder, a couple of the DLL files must have been locked and did not update.

There I saw the error 500 page and on setting of the customErrors mode to be Off, saw the error message mentioned by the OP.

The problem was I did not see the failures listed in the FTP program. I retried those failed fails and they uploaded. The last DLL file updated. So the site then worked.

Upvotes: 0

Dobby432

Reputation: 11

I had the same issue (but on my local) when I was trying to add Entity Framework migration with Package Manager Console.

The way I solved it was by creating a console application where Main() had the following code:

 var dbConfig = new Configuration();
 var dbMigrator = new DbMigrator(dbConfig);
 dbMigrator.Update();

Make sure the Configuration class is the migration Configuration of your failing project. You will need System.Data.Entity.Migrations to use DbMigrator.

Set a breakpoint in your application, and run it. The exception should be caught by Visual Studio (unless you have that exception type set to not break the debug session), and you should be able to find the info you are looking for.

The missing reference in my case was EFProviderWrapperToolkit.

Upvotes: 1

alex440

Reputation: 1657

I had an issue with automap. In the bin folder, the file automap.4net.dll was there, but for some reason the automap.xml and automap.dll weren't. Copying them to the bin directory solved the issue.

Upvotes: 0

Srinivasa Rao

Reputation: 84

I am able to fix this issue by marking "Copy Local=True" on all referenced DLL files in the project, rebuilding and deploying on a testing server.

Upvotes: 0

Shakaron

Reputation: 1065

I had the same error message reported when compiling a Visual Studio package (VSPackage). The whole solution compiles and the error is thrown when the package is being created by CreatePkgDef. Having said that, it is clear that I cannot catch the LoaderExceptions as it is not my application that throws it, but Microsoft's own tool. (Though I am responsible for the confusion of CreatePkgDef.)

In my case the root cause was that my solution creates a MyDll.dll that has already been registered to the GAC (and they are different), so the CreatePgkDef got confused which one to use and it decided just to throw an error which isn't really helpful. The MyDll.dll in the GAC was registered by the installer of the same product (obviously an earlier version, with /slightly/ different content).

How to fix it

Preferred way: Make sure you use the correct version of MyDll.dll
1. When compiling your project make sure you use a different version number than you used in the previous version located in the GAC. Make sure the following attributes are correct:
  - [assembly: AssemblyVersion("1.0.0.1")] // Assuming the old DLL file was versioned 1.0.0.0
  - [assembly: AssemblyFileVersion("1.0.0.1")] // Assuming the old DLL file was versioned 1.0.0.0
2. If needed, specify the fully qualified assembly name (for example, "MyDll.dll, Version=1.0.0.1, Culture=neutral, PublicKeyToken=1234567890abcdef") when you reference it in your other projects.
If the above failed: You can uninstall the old MyDll.dll from GAC
1. How to Uninstall an Assembly from the GAC
2. Uninstall the application that includes MyDll.dll

Changing the AssemblyVersion was good enough for me. :)

I hope this was helpful.

Upvotes: 1

Ilya

Reputation: 1

I build a few projects for SharePoint and, of course, deployed them. One time it happened.

I found an old assembly in C:\Windows\assembly\temp\xxx (with FarManager), removed it after reboot, and all projects built.

I have question for MSBuild, because in project assemblies linked like projects and every assembly is marked "Copy local", but not from the GAC.

Upvotes: 0

Siarhei Kuchuk

Reputation: 5506

Another solution to know why exactly nothing works (from Microsoft connect):

Add this code to the project:

foreach (var asm in AppDomain.CurrentDomain.GetAssemblies())
{
    asm.GetTypes();
}

Turn off generation serialization assemblies.
Build and execute.

Upvotes: 4

amzdmt

Reputation: 181

I also got this issue when create new Microsoft Word add-in with Visual Studio 2015. The issue is about I have 2 versions of MS Office, 2013 and 2016. I uninstall MS Office 2013 and then it works.

Upvotes: 0

Jagan

Reputation: 477

Check this property by clicking 'View Exception Details':

Upvotes: -2

Mentoliptus

Reputation: 2995

I solved this issue by setting the Copy Local attribute of my project's references to true.

Upvotes: 116

Rahul Nikate

Reputation: 6337

This worked for me. Add it in your web.config

<system.web>
  <trust level="Full" />

Upvotes: 2

Ben Gripka

Reputation: 16548

This error has no true magic bullet answer. The key is to have all the information to understand the problem. Most likely a dynamically loaded assembly is missing a referenced assembly. That assembly needs to be in the bin directory of your application.

Use this code to determine what is missing.

using System.IO;
using System.Reflection;
using System.Text;

try
{
    //The code that causes the error goes here.
}
catch (ReflectionTypeLoadException ex)
{
    StringBuilder sb = new StringBuilder();
    foreach (Exception exSub in ex.LoaderExceptions)
    {
        sb.AppendLine(exSub.Message);
        FileNotFoundException exFileNotFound = exSub as FileNotFoundException;
        if (exFileNotFound != null)
        {                
            if(!string.IsNullOrEmpty(exFileNotFound.FusionLog))
            {
                sb.AppendLine("Fusion Log:");
                sb.AppendLine(exFileNotFound.FusionLog);
            }
        }
        sb.AppendLine();
    }
    string errorMessage = sb.ToString();
    //Display or log the error based on your application.
}

Upvotes: 630

Dov Miller

Reputation: 2058

I changed the Specific Version Property of the Refrences to false and that helped.

Upvotes: 1

cat5dev

Reputation: 1335

Verify that each of your projects is setup correctly in the Configuration Manager.

Similar to William Edmondson's reason for this issue, I switched my Configuration Manager setting from "Debug" "Any CPU" to "Debug" ".NET". The problem was that the ".NET" version was NOT configured to build ALL of the projects, so some of my DLLs were out of date (while others were current). This caused numerous problems with starting the application.

The temporary fix was to do Kenny Eliasson's suggestion to clean out the \bin and \obj directories. However, as soon as I made more changes to the non-compiling projects, everything would fail again.

Upvotes: 0

mkorman

Reputation: 978

As it has been mentioned before, it's usually the case of an assembly not being there.

To know exactly what assembly you're missing, attach your debugger, set a breakpoint and when you see the exception object, drill down to the 'LoaderExceptions' property. The missing assembly should be there.

Hope it helps!

Upvotes: 18

Matthew

Reputation: 9949

Adding my specific problem/solution to this as this is the first result for this error message. In my case, the error was received when I deployed a second application within the folder of my first application in IIS. Both were defining connection string with the same name resulting in the child application having a conflict and in turn generating this (to me) non-obvious error message. It was solved by adding:

<clear/>

in the connection string block of the child web application which prevented it from inheriting the connection strings of web.config files higher in the hierarchy, so it looks like:

<connectionStrings>
  <clear/>
  <add name="DbContext" connectionString="MySERVER" providerName="System.Data.SqlClient" />
</connectionStrings>

A reference Stack Overflow question which helped once I determined what was going on was Will a child application inherit from its parent web.config?.

Upvotes: 2

rclopez

Reputation: 11

Other suggestions are all good. In my case, the problem was that the developer box was a 64-bit machine using the x86 location of various APIs, including Silverlight.

By changing the target platform to match the 32-bit server where the web application was being deployed removed the majority of the errors related to not being able to load one or more of the requested types.

Upvotes: 1

Error message &#39;Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.&#39;

Answers (30)

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Error message 'Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.'