I have a problem, while loading DLL at runtime in C#.
Following code:
foreach (var f in Directory.EnumerateFiles(startFolder, "*.dll", SearchOption.AllDirectories))
{
try
{
var assembly = Assembly.LoadFrom(f);
var types = assembly.GetTypes(); //exception raised here
foreach (var type in types)
{
if (type.GetInterface("IPlayerFactory") != null)
instances.Add((IPlayerFactory)Activator.CreateInstance(type));
}
assembly = null;
}
catch (ReflectionTypeLoadException ex) { /* later, keep reading */}
So exception says:
An exception of type 'System.Reflection.ReflectionTypeLoadException' occurred in
mscorlib.dll but was not handled in user code
Additional information: Unable to load one or more of the requested types. Retrieve the
LoaderExceptions property for more information.
I searched stack a little bit and found this catch to look for more information (source: here)
catch block:
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.
Console.WriteLine(sb);
}
So i managed to extract:
'Battleships.Desktop.vshost.exe' (CLR v4.0.30319: Battleships.Desktop.vshost.exe):
Loaded 'C:\SomePath\some_dll.dll'. Cannot find
or open the PDB file.
A first chance exception of type 'System.Reflection.ReflectionTypeLoadException'
occurred in mscorlib.dll
I tried some solutions but nothing works.
Any fresh ideas?
When you build your code in debug mode, two files are created,one the class library and other the 'debug database' .pdb file.if you are running your code in debug mode, include pdb file as well in bin of your reflection code.
Another thing is to look at the Fusion logs using fuslogvw in command prompt.it may give any runtime failures/dependrncies that are not taken care of.
I received the same arcane error ("Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information") while in Release mode, so amolDotnet's solution didn't apply in my situation. For the benefit of anyone else who stumbles upon the same problem, I'll point out that I managed to fix it by adding a missing Nuget package dependency that the DLL needed. T had previously turned off dependency warnings in the Nuget package console and the DLL had functioned just fine, until I tried to load the assembly & inspect the members through Reflection. I might not have found this alternate solution if krzakov hadn't mentioned a deep inspection of the Exception info.
Related
In my codebase, I have created a container sucessfully, but then run into an exception when trying to configure it:
_container = new UnityContainer();
var unityConfigurationSection = (UnityConfigurationSection)ConfigurationManager.GetSection("unity");
if (unityConfigurationSection != null)
{
try
{
unityConfigurationSection.Configure(_container);
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
}
the unityConfigurationSection.Configure(_container); line is what does me in. I get:
The given assembly name or codebase was invalid. (Exception from HRESULT: 0x80131047)
It looks like there's a type that can't be resolved from its name, judging from the stack trace.
But how do I figure out what type?
The exception indicates that the name of the assembly that was requested is in some way not able to be parsed and looked up. If the assembly name was valid but it just wasn't found you'd get a different error.
Usually the message of the exception includes the assembly that failed to resolve.
For instance, this code throws the exact exception:
var asm = Assembly.Load("test,,;''");
This is obviously not a valid assembly name, so you get:
System.IO.FileLoadException: 'Could not load file or assembly '"test\,\,;''"' or one of its dependencies. The given assembly name or codebase was invalid. (Exception from HRESULT: 0x80131047)'
I'd debug the code and see if you can get to the message of the exception.
One thing I'd try is to go into Tools -> Options -> Debugging -> Enable Just My Code and remove the check mark. This should let you see the unwrapped exception that gets thrown when Unity tries to resolve the dependency.
Another quick approach would be to handle the AssemblyResolve Event. Whenever an assembly that was looked for by name fails to resolve for whatever reason that Event is invoked. The args parameter contain the name of the assembly that was tried to be resolved.
Put this as the first line in your Program:
AppDomain.CurrentDomain.AssemblyResolve += Resolver;
and then put this method into the same class:
private static Assembly Resolver(object sender, ResolveEventArgs args)
{
string assemblyName = args.Name;
throw new Exception(args.Name);
}
Now you can set a breakpoint and check out the name of the assembly that tried to get resolved.
I get a error message while updating my service reference:
Custom tool warning: Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.
How can I retrieve the LoaderException property?
Update: My errors went away when I reimported the domain object projects. I have no idea why this fixed the issue, but I'm happy it's working.
try
{
// load the assembly or type
}
catch (Exception ex)
{
if (ex is System.Reflection.ReflectionTypeLoadException)
{
var typeLoadException = ex as ReflectionTypeLoadException;
var loaderExceptions = typeLoadException.LoaderExceptions;
}
}
catch (ReflectionTypeLoadException ex)
{
foreach (var item in ex.LoaderExceptions)
{
MessageBox.Show(item.Message);
}
}
I'm sorry for resurrecting an old thread, but wanted to post a different solution to pull the loader exception (Using the actual ReflectionTypeLoadException) for anybody else to come across this.
Using Quick Watch in Visual Studio you can access the LoaderExceptions from ViewDetails of the thrown exception like this:
($exception).LoaderExceptions
Another Alternative for those who are probing around and/or in interactive mode:
$Error[0].Exception.LoaderExceptions
Note: [0] grabs the most recent Error from the stack
I'm currently at a point where I really need some advice. In our company we mix many languages that are unmanaged like PowerBuilder or pure C++. For now we need a lot of code out of .NET. So my first purpose was why not just make a plugin system via COM.
This is what I'm trying to achieve at the moment. Everything works fine, the plugin system can load plugins. But as soon as I expose my plugin system to COM and try to load a plugin via, as an example VBS, I always get the the following error:
Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information
From my research I found that this problem occurs when, during Assembly.GetTypes(), the type couldn't be loaded. Which is really strange as I have put my interface into it's own assembly and reference it by my plugin system and the plugin, so that the interface is always the same.
But as I debugged a bit more I found that actually the problem seems to not be my interface. The load problem actually happens when he tries to load the type of my class of the plugin which inherits of the interface. Maybe it's the interface or something else.
But to point out for now, as long as I use the plugin system via managed code directly there is no problem. As soon as I do it via COM I receive this error. So I assume that I'm missing or messing something up with COM.
At the moment I really need a solution but not just the solution an explanation of the solution would also be really nice because I actually want to understand what I messed up.
Here is the download link to the solution. Maybe you find someting.
Solution
[ComVisible(true)]
public bool Initialize(string dllPlugin)
{
try
{
string dllPluginPath = Assembly.GetExecutingAssembly().Location.Replace("IncoPluginSystem.dll", "") + "plugins\\";
string completePluginPath = dllPluginPath + dllPlugin + ".dll";
if (!File.Exists(completePluginPath))
{
pluginError = "The plugin could not be found in the plugins directory.";
return false;
}
plugin = Assembly.LoadFile(completePluginPath);
if (plugin == null)
{
pluginError = "No plugin loaded. Pls initialize first";
return false;
}
foreach (Type t in plugin.GetTypes())
{
if (t.GetInterface("IPlugin") != null)
{
pluginInstance = Activator.CreateInstance(t) as IPlugin;
}
}
return true;
}
catch (Exception e)
{
pluginError = e.Message;
return false;
}
}
The Problem happens in the foreach loop where u access the Types of the assembly.
I added a more detailed Exception handling. This is the Error when i expose it to COM
Could not load file or assembly 'IncoPluginSystemInterface, Version-1.0.0.0, Culture=neutral, PuplicKeyToken=497bca4abf979e3e' or one of its dependencies. The system cannot finde the file specified.
Fusion Log:
WRN: Assembly binding logging is turned OFF.
Note: There is some performance penalty associated with assembly bind failure logging.
The references of the DLL are just the standard ones of creating a .net library. Nothing added.
The structure of the plugin system is the following
IncoPluginSystem.dll
IncoPluginSystemInterface.dll
plugins
->IncoPluginSystemInterface.dll
->TestPlugin.dll
So the missing dll is actually at the 2 spots where needed. Maybe it's because the IncoPluginSystem.dll is loaded as a COM object so maybe the path is incorrect but I'm not sure. I tested and changed all I can imagine. So it definitly has to be something I messed up with COM.
I was able to locate the problem. It's actually really that my DLL is in the wrong place. As soon as i put the DLL into the GAC it works. So for now my question is - how can i determine where to put the dll where it was missing. In my exception i only see what dll is missing but not the path. Does anyone know how to determine this?
Ok I was able to answer it myself. To Explain what was wrong. What I did to may help\improve others work in future.
I turned on the FusionLog in the Registry and on the LoaderException I checked for the FusionLog
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();
}
pluginError = sb.ToString();
}
After enabling the FisonLog on the Registry (HKLM\SOFTWARE\Microsoft\Fusion!EnableLog (DWORD 1) I was able to see that the missing DLL is actually needed at the location of the executing program that call's the OLEObject to create an instance of the system via COM.
I wasn't aware of this, but yeah in some way it's rather logic. Luckily i didn't messed up anything on the code it was just in the wrong place.
I am working on some software that will dynamically build menu items for certain dlls so that we can load components in dynamically based on what dlls are available on the users machine. Any dlls that I want to load have been flagged with an Assembly Attribute in the AssemblyInfo.cs file and how I determine whether or not I want to build a menu item for that dll. Here is my method so far:
private void GetReportModules() {
foreach (string fileName in Directory.GetFiles(Directory.GetCurrentDirectory())) {
if (Path.GetExtension(fileName) == ".dll" || Path.GetExtension(fileName) == ".exe") {
System.Reflection.Assembly assembly = System.Reflection.Assembly.LoadFrom(fileName);
object[] attributes = assembly.GetCustomAttributes(typeof(ReportNameAttribute), false);
if (attributes.Count() > 0) {
ReportNameAttribute reportNameAttribute = attributes[0] as ReportNameAttribute;
Type type = assembly.GetType(reportNameAttribute.BaseType);
MenuItem customReportsMenuItem = new MenuItem();
customReportsMenuItem.Header = reportNameAttribute.ReportName;
ReportsMenuItem.Items.Add(customReportsMenuItem);
customReportsMenuItem.Click += (s, ev) => {
var obj = Activator.CreateInstance(type);
type.InvokeMember("Show", System.Reflection.BindingFlags.Default | System.Reflection.BindingFlags.InvokeMethod, null, obj, null);
};
}
}
}
}
For the most part its working fine, I am getting the dlls that I am expecting back out and am creating my menu items fine. The problem is that in order to check for the attribute I first need to load the assembly using Reflection. Some of the other local dlls are throwing errors when I try to load them about missing dependencies or he module was expected to contain an assembly manifest. Is there a way I can safely check to see if an assembly CAN be loaded before I actually do so? (sounds stupid as I write it out). Any thoughts on the problem I'm running into or better suggestions for how to accomplish what I'm trying here? Feeling a little bit in over my head.
You can create a separate AppDomain, try to load the assemblies there, send the results back, and unload the AppDomain. This way you do not change your current AppDomain with 'garbage' of any loaded assemblies.
One way would be to make use of a try catch block. If it throw's an exception, you're not interested...
EDIT:
MSDN explains clearly the type of exceptions LoadFrom can throw. FileLoadException looks likely in your case.
I'm sure there is code out there that carried on after a catch. For example a logging framework. I would not want my framework to catch an exception and make my executable stop etc, i'd want it to smother the exception. My application should not fail just because a line of log miss fired.
You can try the Unmanaged Metadata API (http://msdn.microsoft.com/en-us/library/ms404384.aspx) or the Common Compiler Infrastructure Metadata API (http://ccimetadata.codeplex.com/) as alternatives to plain reflection.
I get a error message while updating my service reference:
Custom tool warning: Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.
How can I retrieve the LoaderException property?
Update: My errors went away when I reimported the domain object projects. I have no idea why this fixed the issue, but I'm happy it's working.
try
{
// load the assembly or type
}
catch (Exception ex)
{
if (ex is System.Reflection.ReflectionTypeLoadException)
{
var typeLoadException = ex as ReflectionTypeLoadException;
var loaderExceptions = typeLoadException.LoaderExceptions;
}
}
catch (ReflectionTypeLoadException ex)
{
foreach (var item in ex.LoaderExceptions)
{
MessageBox.Show(item.Message);
}
}
I'm sorry for resurrecting an old thread, but wanted to post a different solution to pull the loader exception (Using the actual ReflectionTypeLoadException) for anybody else to come across this.
Using Quick Watch in Visual Studio you can access the LoaderExceptions from ViewDetails of the thrown exception like this:
($exception).LoaderExceptions
Another Alternative for those who are probing around and/or in interactive mode:
$Error[0].Exception.LoaderExceptions
Note: [0] grabs the most recent Error from the stack