We Keep Coding

How to Load a dll file in SSIS That ins't in the GAC

I am trying to load a dll in a SSIS project that ins't in a GAC. I followed the following code from here
the code:
[Microsoft.SqlServer.Dts.Tasks.ScriptTask.SSISScriptTaskEntryPointAttribute]
public partial class ScriptMain : Microsoft.SqlServer.Dts.Tasks.ScriptTask.VSTARTScriptObjectModelBase
{
static ScriptMain()
{
AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(CurrentDomain_AssemblyResolve);
}
static System.Reflection.Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
{
if (args.Name.Contains("ssisHelper"))
{
string path = #"c:\temp\";
return System.Reflection.Assembly.LoadFile(System.IO.Path.Combine(path, "ssisHelper.dll"));
}
return null;
}
}
This enabled the loading of the dll but it keep giving me the following error because Entity Framework was referenced inside the dll.
Could not load file or assembly 'EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' or one of its dependencies. The system cannot find the file specified.
So I tried to set the Working directory of dll with no success because dll's don't have an entry point. So I got the idea to put the file in a console application from here. I built an .exe and changed it to a .dll. Now in theory I have an entry point where I could set the working directory.
System.Environment.CurrentDirectory = #"PathToDll";
Yet I still get the same error. Does any one know of a solution?

Try to add an else if clause for each Assembly name:
static System.Reflection.Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
{
if (args.Name.Contains("ssisHelper"))
{
string path = #"c:\temp\";
return System.Reflection.Assembly.LoadFile(System.IO.Path.Combine(path, "ssisHelper.dll"));
}
else if (args.Name.Contains("xxx"))
{
string path = #"c:\temp\";
return System.Reflection.Assembly.LoadFile(System.IO.Path.Combine(path, "xxx.dll"));
}; return null;

Resolve dependency when an assembly is loaded using Assembly.Load(byte[])

I use Assembly.Load(byte[]) to load an assembly. This loaded assembly internally uses codeDomProvider.CompileAssemblyFromSource() to compile code which is failing with error 'The type or namespace name '<ClassName>' could not be found (are you missing a using directive or an assembly reference?)'.
AppDomain.AssemblyResolve event is not fired for the references present in the code to compile.
FYI: I am trying to load assembly which uses FileHelpers.dll and it calls on ClassBuilder.ClassFromString function. Assembly load fails with RunTimeCompilationException.
How should I resolve such dependencies?
UPDATE:
Here is code I am using
ctor()
{
AppDomain.CurrentDomain.AssemblyResolve += CurrentDomainOnAssemblyResolve;
}
private Assembly CurrentDomainOnAssemblyResolve(object sender, ResolveEventArgs args)
{
AssemblyName assemblyName = new AssemblyName(args.Name);
return LoadAssembly(assemblyName);
}
public Assembly GetAssembly(string assemblyFullName)
{
AssemblyName assemblyName = new AssemblyName(assemblyFullName);
Assembly assembly = LoadAssembly(assemblyName) ?? Assembly.Load(assemblyName);
}
private Assembly LoadAssembly(AssemblyName assemblyName)
{
byte[] assemblyBytes = GetAssemblyBytes(); // Get assembly bytes from external source
return Assembly.Load(assemblyBytes);
}
Thanks
Yash

You need to handle the CurrentDomain.ResolveEventHandler event as below, this event will be triggered whenever a reference is required:
code to load assemblies:
private void LoadAssem(){
AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(CurrentDomain_AssemblyResolve);
//use File.ReadAllBytes to avoid assembly locking
Assembly asm2 = Assembly.Load(File.ReadAllBytes("AssemblyPath"));
}
Once a reference is needed it will call the below event:
private static string asmBase;
//asmBase contains the folder where all your assemblies found.
public static Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
{
//This handler is called only when the common language runtime tries to bind to the assembly and fails.
//Retrieve the list of referenced assemblies in an array of AssemblyName.
Assembly MyAssembly, objExecutingAssemblies;
string strTempAssmbPath = "";
objExecutingAssemblies = args.RequestingAssembly;
AssemblyName[] arrReferencedAssmbNames = objExecutingAssemblies.GetReferencedAssemblies();
//Loop through the array of referenced assembly names.
foreach (AssemblyName strAssmbName in arrReferencedAssmbNames)
{
//Check for the assembly names that have raised the "AssemblyResolve" event.
if (strAssmbName.FullName.Substring(0, strAssmbName.FullName.IndexOf(",")) == args.Name.Substring(0, args.Name.IndexOf(",")))
{
//Build the path of the assembly from where it has to be loaded.
strTempAssmbPath = asmBase + "\\" + args.Name.Substring(0, args.Name.IndexOf(",")) + ".dll";
break;
}
}
//Load the assembly from the specified path.
MyAssembly = Assembly.Load(File.ReadAllBytes(strTempAssmbPath));
//Return the loaded assembly.
return MyAssembly;
}

Create custom AppDomain and add assemblies to it

How can I create an appdomain, add assemblies to it, then destroy that app domain? This is what I have tried:
static void Main(string[] args)
{
string pathToExe = #"A:\Users\Tono\Desktop\ConsoleApplication1.exe";
AppDomain myDomain = AppDomain.CreateDomain("MyDomain");
Assembly a = Assembly.Load(System.IO.File.ReadAllBytes(pathToExe));
myDomain.Load(a.FullName); // Crashes here!
}
I have also tried:
myDomain.Load(File.ReadAllBytes(pathToExe));
how can I add an assembly to the appdomain. Once I do that I can find the method via reflection execute it and then destroy the appdomain
The exception that I get is:
Could not load file or assembly 'ConsoleApplication1, Version=1.0.0.0,
Culture=neutral, PublicKeyToken=null' or one of its dependencies. The
system cannot find the file specified.

Two quick points:
AppDomain.Load loads an assembly in the current AppDomain and not on myDomain (weird, I know).
AppDomain.Load loads an assembly in the Load context, which resolves assemblies from the apps base-dir, the private-bin-paths and the GAC. Most probably, the assembly you try to load is not located in any of these locations which explains the exception message.
For more info have a look at this answer.
One way to load assemblies to an AppDomain is by creating a MarshalByRef-derived loader. You need something like this to avoid leaking types (and assemblies) to your main AppDomain. Here's a simple one:
public class SimpleAssemblyLoader : MarshalByRefObject
{
public void Load(string path)
{
ValidatePath(path);
Assembly.Load(path);
}
public void LoadFrom(string path)
{
ValidatePath(path);
Assembly.LoadFrom(path);
}
private void ValidatePath(string path)
{
if (path == null) throw new ArgumentNullException("path");
if (!System.IO.File.Exists(path))
throw new ArgumentException(String.Format("path \"{0}\" does not exist", path));
}
}
And use it like that:
//Create the loader (a proxy).
var assemblyLoader = (SimpleAssemblyLoader)myDomain.CreateInstanceAndUnwrap(typeof(SimpleAssemblyLoader).Assembly.FullName, typeof(SimpleAssemblyLoader).FullName);
//Load an assembly in the LoadFrom context. Note that the Load context will
//not work unless you correctly set the AppDomain base-dir and private-bin-paths.
assemblyLoader.LoadFrom(pathToExe);
//Do whatever you want to do.
//Finally unload the AppDomain.
AppDomain.Unload(myDomain);

AssemblyResolve event fires when calling Assembly.Load(byte())

So I have a WPF project that is pulling in dlls that are used by another project here at my job. It's a mess of dependencies, I've been using the technique here: http://www.digitallycreated.net/Blog/61/combining-multiple-assemblies-into-a-single-exe-for-a-wpf-application to embed the dependencies into a single executable.
Now, when I'm calling a specific method inside one of the dependencies, I hit the AssemblyResolve event. My OnResolveAssembly event runs, it finds the assembly as an embedded resource (cool!), and does "return Assembly.Load(assembyRawBytes)". If I hit F11 at this point (with a breakpoint at the beginning of OnResolveAssembly), I get another call into the same event. It's for the same assembly too (args.Name is the same).
If I let this run I hit a stack overflow, since I can never seem to escape this recursive event calling.
The MSDN docs don't really say when Assembly.Load can fail, except with a FileNotFoundException or BadImageFormatException.
I've tried unhooking the OnResolveAssembly at the moment before I call Assembly.Load, but then my application dies a mysterious death, even under VS it just goes poof.
I'm probably breaking several rules here, but some ideas of where to start looking for problems would be welcome.
I'm going to start poking around in the problematic DLL to see if there are hints about what is wrong with it (maybe it's a mixed assembly?).
Here's my OnResolveAssembly handler:
private static Assembly OnResolveAssembly(object sender, ResolveEventArgs args)
{
Assembly executingAssembly = Assembly.GetExecutingAssembly();
AssemblyName assemblyName = new AssemblyName(args.Name);
string path = assemblyName.Name + ".dll";
if (assemblyName.CultureInfo.Equals(System.Globalization.CultureInfo.InvariantCulture) == false)
{
path = String.Format(#"{0}\{1}", assemblyName.CultureInfo, path);
}
using (Stream stream = executingAssembly.GetManifestResourceStream(path))
{
if (stream == null)
return null;
byte[] assemblyRawBytes = new byte[stream.Length];
stream.Read(assemblyRawBytes, 0, assemblyRawBytes.Length);
assemblyDictionary.Add(assemblyName.Name, Assembly.Load(assemblyRawBytes));
return assemblyDictionary[assemblyName.Name];
}
}
For the time being, I've resolved it by iterating through all of my resources and attempting Assembly.Load on them, and storing them in a dictionary for retrieval (during the OnResolveAssembly event):
[STAThread]
public static void Main()
{
AppDomain.CurrentDomain.AssemblyResolve += OnResolveAssembly;
Assembly executingAssembly = Assembly.GetExecutingAssembly();
string[] resources = executingAssembly.GetManifestResourceNames();
foreach (string resource in resources)
{
if (resource.EndsWith(".dll"))
{
using (Stream stream = executingAssembly.GetManifestResourceStream(resource))
{
if (stream == null)
continue;
byte[] assemblyRawBytes = new byte[stream.Length];
stream.Read(assemblyRawBytes, 0, assemblyRawBytes.Length);
try
{
assemblyDictionary.Add(resource, Assembly.Load(assemblyRawBytes));
}
catch (Exception ex)
{
System.Diagnostics.Debug.Print("Failed to load: " + resource + " Exception: " + ex.Message);
}
}
}
}
App.Main();
}
private static Assembly OnResolveAssembly(object sender, ResolveEventArgs args)
{
Assembly executingAssembly = Assembly.GetExecutingAssembly();
AssemblyName assemblyName = new AssemblyName(args.Name);
string path = assemblyName.Name + ".dll";
if (assemblyDictionary.ContainsKey(path))
{
return assemblyDictionary[path];
}
return null;
}
It seems be working fine now (the "failing" assembly will load fine in my second snippet), but I'd be interested to learn why it doesn't work in the first.

Loading an assembly from byte[] is a good way to end up in .dll hell (the place you go for too many/complex dependencies). Problem here is that although you loaded the dll to an AppDomain it is not automatically resolved, when you need it again for dependent types.
I commented on this problem here: AssemblyResolve Does not fire
Long story short, Assemblies are loaded into different "contexts" inside of AppDomains. The context used by Load(byte[]) does not resolve Assemblies automatically.
The solution is keeping track of the loaded assemblies and returning the already loaded assembly instead of loading it a second time. There is a starting point to this approach in my answer to:
Need to hookup AssemblyResolve event when DisallowApplicationBaseProbing = true
But I think you got it right with your workaround.
BTW. Loading an assembly twice is a way to get identical but incompatible types. Ever cast an object of MyType from MyAssembly into MyType from the very same assembly and got null?
That's a warm "Welcome to .dll hell".

AppDomain.CurrentDomain.AssemblyResolve asking for a <AppName>.resources assembly?

using the code How to embed a satellite assembly into the EXE file provided by csharptest.net, I've created a custom assembly resolver and embedded my assemblies in my resources.
I can successfully resolve my assemblies used in but somehow AppDomain.CurrentDomain.AssemblyResolve asks for an assembly called 'AppName.resources' specifically "MyProgram.resources, Version=0.15.3992.31638, Culture=en-US, PublicKeyToken=null" which i don't know how to resolve?
I've tried to disable loading my custom assemblies from resources (placed all my assembly dll's in program directory) and just enabled AppDomain.CurrentDomain.AssemblyResolve, but it was still asking for it.
I'm a bit confused about this, will appreciate a lot if you can help me on this.
Here's my code for interested ones;
static Assembly ResolveAssemblies(object sender, ResolveEventArgs args)
{
Assembly assembly = null;
string name = args.Name.Substring(0, args.Name.IndexOf(','));
if (name == "MyProgram.resources") return null;
else name = string.Format("MyProgram.Resources.Assemblies.{0}.dll", name);
lock (_loadedAssemblies)
{
if (!_loadedAssemblies.TryGetValue(name, out assembly))
{
using (Stream io = Assembly.GetExecutingAssembly().GetManifestResourceStream(name))
{
if (io == null)
{
MessageBox.Show("MyProgram can not load one of it's dependencies. Please re-install the program", string.Format("Missing Assembly: {0}", name), MessageBoxButtons.OK, MessageBoxIcon.Error);
Environment.Exit(-1);
}
using (BinaryReader binaryReader = new BinaryReader(io))
{
assembly = Assembly.Load(binaryReader.ReadBytes((int)io.Length));
_loadedAssemblies.Add(name, assembly);
}
}
}
}
return assembly;
}

Answering on my own;
Adding this line to AssemblyInfo.cs solves it and resolver will not get asked for resources any-more.
[assembly: NeutralResourcesLanguageAttribute("en-US", UltimateResourceFallbackLocation.MainAssembly)]
Though this is a work-around should be carefully considered multi-language applications.
More Info:
https://connect.microsoft.com/VisualStudio/feedback/details/526836/wpf-appdomain-assemblyresolve-being-called-when-it-shouldnt
http://blogs.msdn.com/b/kimhamil/archive/2008/11/11/what-does-the-neutralresourceslanguageattribute-do.aspx
http://forums.devshed.com/net-development-87/c-wpf-appdomain-assemblyresolve-being-called-when-it-shouldn-t-669567.html
http://blogs.msdn.com/b/microsoft_press/archive/2010/02/03/jeffrey-richter-excerpt-2-from-clr-via-c-third-edition.aspx
This approach fails for machines with non en-US cultures. A better approach is ignoring resources on assembly resolver;
public Assembly Resolver(object sender, ResolveEventArgs args)
{
lock (this)
{
Assembly assembly;
AssemblyName askedAssembly = new AssemblyName(args.Name);
string[] fields = args.Name.Split(',');
string name = fields[0];
string culture = fields[2];
// failing to ignore queries for satellite resource assemblies or using [assembly: NeutralResourcesLanguage("en-US", UltimateResourceFallbackLocation.MainAssembly)]
// in AssemblyInfo.cs will crash the program on non en-US based system cultures.
if (name.EndsWith(".resources") && !culture.EndsWith("neutral")) return null;
/* the actual assembly resolver */
...
}
}

My situation was a bit more complex and the above solution did not work for me. (That is changing the AssemblyInfo.cs file)
I have moved all my form and image resources to a seperate dll and the moment any of the images are used the 'filenotfoundexception' exception is thrown.
The important information is the following:
Beginning with the .NET Framework 4, the ResolveEventHandler event is raised for all assemblies, including resource assemblies. See the following reference
https://msdn.microsoft.com/en-us/library/system.appdomain.assemblyresolve(v=vs.110).aspx
The solution turned out to be very simple. If a resource file is requested in the form 'dllname.resources.dll' always return null;
Here is the event code that I have adapted from other samples found. (I have commented the debugging lines - un-comment them if you have a problem using the code.
Add this line in your class. It is used to prevent loading a dll more than once
readonly static Dictionary<string, Assembly> _libs = new Dictionary<string, Assembly>();
This is the event method.
private static Assembly OnAssemblyResolve(object sender, ResolveEventArgs args)
{
Assembly assembly = null;
string keyName = new AssemblyName(args.Name).Name;
if (keyName.Contains(".resources"))
{
return null; // This line is what fixed the problem
}
if (_libs.ContainsKey(keyName))
{
assembly = _libs[keyName]; // If DLL is loaded then don't load it again just return
return assembly;
}
string dllName = DllResourceName(keyName);
//string[] names = Assembly.GetExecutingAssembly().GetManifestResourceNames(); // Uncomment this line to debug the possible values for dllName
using (Stream stream = Assembly.GetExecutingAssembly().GetManifestResourceStream(dllName))
{
if (stream == null)
{
Debug.Print("Error! Unable to find '" + dllName + "'");
// Uncomment the next lines to show message the moment an assembly is not found. (This will also stop for .Net assemblies
//MessageBox.Show("Error! Unable to find '" + dllName + "'! Application will terminate.");
//Environment.Exit(0);
return null;
}
byte[] buffer = new BinaryReader(stream).ReadBytes((int) stream.Length);
assembly = Assembly.Load(buffer);
_libs[keyName] = assembly;
return assembly;
}
}
private static string DllResourceName(string ddlName)
{
if (ddlName.Contains(".dll") == false) ddlName += ".dll";
foreach (string name in Assembly.GetExecutingAssembly().GetManifestResourceNames())
{
if (name.EndsWith(ddlName)) return name;
}
return ddlName;
}