I have a very weird problem with Unity here. I have the following:
public class UnityConfig
{
public static void RegisterTypes(IUnityContainer container)
container.RegisterType<IDBContext, MyDbContext>(new PerThreadLifetimeManager());
container.RegisterType<IUserDbContext>(new PerThreadLifetimeManager(), new InjectionFactory(c =>
{
var tenantConnectionString = c.Resolve<ITenantConnectionResolver>().ResolveConnectionString();
return new UserDbContext(tenantConnectionString);
}));
}
}
and then in the WebApiConfig.cs file within the Reigster method:
var container = new UnityContainer();
UnityConfig.RegisterTypes(container);
config.DependencyResolver = new UnityResolver(container);
Basically, what I want to happen in the above code is on every request to the API, I want Unity to new up a UserDbContext based on the user (multi-tenant kind of environment). Now the TenantConnectionResolver is responsible for figuring out the Connection String and then I use that connection string to new up UserDbContext.
Also note (not shown above) that TenantConnectionResolver takes an IDbConext in its constructor because I need it to figure out the connection string based on user information in that database.
But for some reason, the code within the InjectionFactory runs at random times. For example, I call //mysite.com/controller/action/1 repetitively from a browser, the code in the InjectionFactory will occasionally run but not on each request.
Am I incorrectly configuring Unity? Has anybody encountered anything similar to this?
Thanks in advance
The problem is very likely related to the LifetimeManager you are using. PerThreadLifetimeManager is not adapted in a web context, as threads are pooled and will serve multiple requests in sequence.
PerRequestLifetimeManager is probably what you want to use.
please excuse the long description at the beginning. the questions are at the end.
i have a windows service that is supposed to read data form some data sources (represented by the IDataSource interface).
i'm using MEF in my project and i was thinking of injecting the required data sources via ctor injection like below:
[Export(typeof(Service))]
public class Service:ServiceBase{
[ImportingConstructor]
public Service([ImportMany]IEnumerable<IDataSource> dataSources){
//...
}
}
However, there is a problem in doing it like this. The service needs to use any combination of data sources: multiple data sources of the same type (ex: 2 CSVDataSource instances) or multiple data sources of different types (ex: 2 CSVDataSource instances and 1 SQLDataSource instance).
Each data source has properties that are retrieved from the DB in order to properly set it up. these settings might indicate from where to read the data and at what intervals. this is why, in my implementation, the data sources have a ctor that accepts an id. this id is used to identify the data source in the DB and to retrieve the specific data source settings from the DB. this can be seen below.
public class CSVDataSource: IDataSource{
public CSVDataSource(int dsId){
//call web service in order to get properties to
//properly set up the data source.
}
//...
}
i feel that the service definition presented above is not suited for this scenario. The other approach I can think of is to use some sort of factory that allows the service to dynamically create the data sources inside. this implementation might look like below.
public class Service:ServiceBase{
[ImportingConstructor]
public Service(IDataSourceFactory dsFactory)
{
if (dsFactory == null) throw new ArgumentNullException("dsFactory");
IEnumerable<IDataSource> dataSources = dsFactory.CreateAll();
}
}
[Export(typeof(IDataSourceFactory))]
[PartCreationPolicy(CreationPolicy.Shared)]
public class DataSourceFactory:IDataSourceFactory
{
private readonly int agentId;
[ImportingConstructor]
public DataSourceFactory([Import("AgentId")]int agentId)
{
this.agentId = agentId;
}
public IEnumerable<IDataSource> CreateAll()
{
List<IDataSource> dataSources = new List<IDataSource>();
//access web service and instantiate the data sources
return dataSources;
}
}
And now to my questions:
is my factory approach a good ideea or should i look for another approach?
is it ok to have exports that require data from a remote location in order to be created?
Did you come across ExportMetadataAttribute before? It will allow you to assign metadata to an export that you can view before the export is created. You'll be able to import your IDataSources as Lazy and then should be able to create them yourself with the required parameters.
There's a good breakdown of Lazy and ExportMetadata here
My service will load a lot of data (from txt files) to memory every request.
But,I want to keep the data in memory.
Because it is read from same txt files.
public class pirTMain {
public String[] RUN_pirT(...){
...
//this object will read txt files to initialize
ELC elc = new ELC(elcFolder.getPath());
//use elc to initialize a graph
pirT.initGraph(userID, nodeFile.getPath(), userScore, elc, true, begin, target);
//Use graph to search paths
itinerary = pirT.search(userID, TopK, begin, beginWithTime, target, targetWithTime);
...
I had read Axis2 document.
It says I can change service scope to "application".
But I still don't know how to do it, because I use eclipse plugin to generate a web service *.arr.
Can anyone suggest me how to separate elc object to another service?
Then, my pirTMain class can use it.
pirTMain is 'request'.
elc is 'application'.
thanks a lot.
There are a lot of different ways to achieve this, the simplest one that comes in my mind is to create a static reference to the read lines so that it's shared among all threads in the same virtual machine:
#WebService
public MyServiceClass {
private static String[] readLines = null;
private static synchronized getLines(){
if (readLines == null)
readLines = ....;
return readLines;
}
public int getNumberOfLines(){
return MyServiceClass.getLines().length;
}
public String getLine(int position){
return MyServiceClass.getLines()[position];
}
...
}
Probably not the "cleanest" way, but it works and it's easy to do. You could also wrap the login in a more standard "singleton pattern" if you prefer. keep in mind that getLines should be synchronized to be thread safe but if you experience bottlenecks remove the synchronized keyword, you could get useless reads on first calls but it would be faster.
this post ideally continues my other post on MEF plugins, but my first post was too full of comments and this sample is more complete. Here I summarize my updated scenario, with all my findings up to this point. Hope this can be useful to other CM newbies like me.
You can download a full repro sample scenario: it's an almost do-nothing dumb skeleton for a CM + MEF plugins-based application:
VS2010 repro solution (updated)
This is a minimal stripped down solution representing my issues with CM+MEF.
There are 3 projects:
the main UI (CmRepro).
a core DLL shared among all the addins (AddinCore), with a couple of interfaces and custom attributes used for MEF metadata.
a sample addin DLL (AlphaAddin), with a view and a viewmodel implementing the interfaces.
The core contains 2 interfaces representing a viewmodel and its view, and 2 attributes to be used for decorating the viewmodels and the views. The viewmodel interface describes a class which should compose a greeting message from some person name, so it exposes a couple of properties and a method for this. The view interface just exposes a property returning its DataContext cast to the viewmodel interface.
The sample addin has an implementation for a viewmodel and a view; both are MEF-exports, decorated by the corresponding attribute. In the real-world solution several properties of these attributes are used for filtering; here I just have a dummy Language property which should allow for other plugins for different languages.
The main UI has a MEF bootstrapper which adds code for retrieving MEF exports from an Addins folder. I modified this code to include exports from MEF directories and get a better understanding of some MEF exceptions, but still I cannot figure out how to properly "register" them with CM.
The main viewmodel has 2 methods: one (A) uses a MEF catalog to retrieve a viewmodel and its view, bind them and show them into a window. Another (B) uses the same catalog to get a viewmodel, and then a CM window manager to locate, create, bind and show the corresponding view according to CM naming conventions. These methods represent two alternative ways I should deal with in my real-world code, i.e. instantiating some crucial objects "by myself" just using MEF but then let them work for CM, or letting CM (with a MEF-bootstrapper) do most of the work starting from a viewmodel.
Anyway, it seems that in both cases I am missing something as for registration with CM. Issues:
(A) how do I wire up VM+V for CM so that the conventions for databinding etc are applied? At this time I can build my MEF parts together, but CM ignores them as it was not used to instantiate none of them.
I answer to myself here:
ViewModelBinder.Bind(viewmodel, (UserControl)view, null);
(B) how do I register the exports from MEF in CM so that the CM window manager can find the view? Currently it does not manage to locate the view from the viewmodel.
Addition (21 jun)
I try to explain better for whom cannot access the repro solution. I use a "standard" MEF bootstrapper, changing the Configure override like:
_container = new CompositionContainer(
new AggregateCatalog(AssemblySource.Instance.Select(
x => new AssemblyCatalog(x)).OfType()
.Union(GetAddinDirectoryCatalogs())));
this creates a MEF composition container which aggregates the catalog from AssemblySource, with CM types like event aggregator or window manager, with a catalog from several addin directories, which contain exports for both V and VM's.
In my sample main viewmodel I create a new VM from a plugin, found in the host application directory among others, and I'd like a CM window manager to locate, instantiate and show its view in a dialog, e.g.:
viewmodel = GetMyViewModelFromAddin();
windowmanager.ShowDialog(viewmodel);
CM anyway cannot locate the view. AFAIK, naming conventions are honored: both V and VM are in the same addin assembly, marked as MEF exports, named like SomethingViewModel / SomethingView. Anyway, as Leaf pointed out in his clarification, AssemblySource.Instance is a static IObservableCollection collection of assemblies and I have not added my addins to it. But this is right the point: I would not like to add all of them in advance, because this means loading ALL the addins without yet knowing which (if any) will be ever used. A robust plugin system is the reason for using MEF, after all. I'm new to CM and not sure if it is possible (and where) to find an extension point for CM in this scenario. The window manager does not call my bootstrapper implementation at all, clearly because there is nothing to be instantiated by IoC, as no match was found in assembly source Instance. So, it seems I'm stuck here, the only solution being loading in advance all the assemblies in the Instance, but this seems defeating the whole purpose of using MEF.
The plugin-based application I'm developing loads tons of V+VM CM "pairs" representing user interface widgets, which in turn often use a window manager to popup other V+VM's pairs as dialogs. I can bypass instantiation by CM and use MEF to retrieve V+VM for each widget, but still I'm facing the same view location issue for each widget requiring a window manager. The other alternative (workaround) I can see is avoding the use of window manager and implement my own mechanism for the purpose of showing dialogs from widgets, but this makes feel me a little wrong about CM...:). Usually when I find myself writing much more code than expected I am inclined to think I'm not using the tool in the right way. Any idea?
Caliburn.Micro goes through 3 stages to find a view from a viewmodel instance.
Does text transforms to transform view type name to viewmodel type name. There are a set of standard conventions for these transformations, e.g. SomeNamespace.ViewModels.CustomerViewModel might map to SomeNamespace.Views.CustomerView.
With the view type name(s), Caliburn.Micro then uses AssemblySource.Instance (a static IObservableCollection<Assembly> collection of assemblies) to find the first matching Type.
Caliburn.Micro attempts to create an instance of that Type via one of the IoC.GetInstance() methods (which delegate to your bootstrapper and hence MEF).
I'm guessing (your file share site is blocked here) that the problem with resolving views from viewmodels is due to the second step and the AssemblySource.Instance collection not containing your dynamic assembly.
One solution might be to add each dynamically loaded addin's assembly to AssemblySource.Instance when they are loaded, or if you know all assemblies at startup then you can override the Bootstrapper.SelectAssemblies method to return list of assemblies you expect to contain views and viewmodels.
Update to show how you could pull assemblies from MEF loaded parts
If you are using DirectoryCatalog to load your parts from other assemblies then you could find the assemblies used like this:
var directoryCatalog = new DirectoryCatalog(#"./");
AssemblySource.Instance.AddRange(
directoryCatalog.Parts
.Select(part => ReflectionModelServices.GetPartType(part).Value.Assembly)
.Where(assembly => !AssemblySource.Instance.Contains(assembly)));
If your addins folder changes during the runtime of the application then you would have to DirectoryCatalog.Refresh() the catalog and run the code to add any new assemblies to AssemblySource.Instance
I found a workaround. It's not that pretty, but it allows CM and its window manager to work. I summarize here my findings, hope this will help others or let someone point me to a better solution.
Given that (a) I do not want to load ALL the assemblies including all their dependencies in my plugins folder, to avoid polluting my app domain with unused stuff; and that (b) the only available CM extension point for this seems SelectAssemblies, my goal is add my assemblies there, but only the plugin assemblies requiring to be registered with CM.
So I started looking for a way of loading all the DLL's into a temporary app domain, scan them for some aspect marking them as plugins, and then load into the current app domain only the plugin ones, passing them to SelectAssemblies. This is far from being the optimal solution, as I cannot use a general purpose scanning way like MEF, and I feel I'm duplicating the effort, but at least it's a working solution.
First, to provide at least a way for loading only the plugins, I decorate my plugin assemblies requiring CM registration with a custom attribute marking them as plugins, and further enumerate their types looking for the ones which should be later used by MEF.
The attribute is as simple as:
[AttributeUsage(AttributeTargets.Assembly)]
public class AssemblyRegisteredWithCMAttribute : Attribute {}
I then found this very good piece of code for scanning assemblies into another temporary AppDomain:
http://sachabarber.net/?p=560
I had to modify it a bit, because it was failing when loading assemblies with dependencies, and it was scanning the assemblies types while in my case I just need to check for the attribute.
Here is my code:
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Policy;
using System.Reflection;
using System.Diagnostics.CodeAnalysis;
namespace CmRepro
{
///
/// Separate AppDomain assembly loader.
///
/// Modified from http://sachabarber.net/?p=560 .
public class SeparateAppDomainAssemblyLoader
{
///
/// Loads an assembly into a new AppDomain returning the names of the files
/// containing assemblies marked with the assembly attribute name matching
/// the specified name. The new AppDomain is then Unloaded.
///
/// list of files to load
/// assemblies directory
/// matching attribute name
/// list of found namespaces
/// null files, assembly directory or matching attribute
public List LoadAssemblies(string[] aFiles, string sAssemblyDirectory, string sMatchingAttribute)
{
if (aFiles == null) throw new ArgumentNullException("aFiles");
if (sAssemblyDirectory == null) throw new ArgumentNullException("sAssemblyDirectory");
if (sMatchingAttribute == null) throw new ArgumentNullException("sMatchingAttribute");
List<String> namespaces = new List<String>();
AppDomain childDomain = BuildChildDomain(AppDomain.CurrentDomain);
try
{
Type loaderType = typeof(AssemblyLoader);
if (loaderType.Assembly != null)
{
AssemblyLoader loader = (AssemblyLoader)childDomain.
CreateInstanceFrom(
loaderType.Assembly.Location,
loaderType.FullName).Unwrap();
namespaces = loader.LoadAssemblies(aFiles, sAssemblyDirectory, sMatchingAttribute);
} //eif
return namespaces;
}
finally
{
AppDomain.Unload(childDomain);
}
}
/// <summary>
/// Creates a new AppDomain based on the parent AppDomains
/// Evidence and AppDomainSetup.
/// </summary>
/// <param name="parentDomain">The parent AppDomain</param>
/// <returns>A newly created AppDomain</returns>
private AppDomain BuildChildDomain(AppDomain parentDomain)
{
Evidence evidence = new Evidence(parentDomain.Evidence);
AppDomainSetup setup = parentDomain.SetupInformation;
return AppDomain.CreateDomain("DiscoveryRegion", evidence, setup);
}
/// <summary>
/// Remotable AssemblyLoader, this class inherits from <c>MarshalByRefObject</c>
/// to allow the CLR to marshall this object by reference across AppDomain boundaries.
/// </summary>
private class AssemblyLoader : MarshalByRefObject
{
private string _sRootAsmDir;
/// <summary>
/// ReflectionOnlyLoad of single Assembly based on the assemblyPath parameter.
/// </summary>
/// <param name="aFiles">files names</param>
/// <param name="sAssemblyDirectory">assemblies directory</param>
/// <param name="sMatchingAttribute">matching attribute name</param>
[SuppressMessage("Microsoft.Performance", "CA1822:MarkMembersAsStatic")]
internal List<string> LoadAssemblies(string[] aFiles, string sAssemblyDirectory, string sMatchingAttribute)
{
AppDomain.CurrentDomain.ReflectionOnlyAssemblyResolve += OnReflectionOnlyAssemblyResolve;
_sRootAsmDir = sAssemblyDirectory;
List<string> aAssemblies = new List<String>();
try
{
sMatchingAttribute = "." + sMatchingAttribute;
foreach (string sFile in aFiles)
Assembly.ReflectionOnlyLoadFrom(sFile);
aAssemblies.AddRange(from asm in AppDomain.CurrentDomain.ReflectionOnlyGetAssemblies()
let attrs = CustomAttributeData.GetCustomAttributes(asm)
where attrs.Any(a => a.ToString().Contains(sMatchingAttribute))
select asm.FullName);
return aAssemblies;
}
catch (FileNotFoundException)
{
/* Continue loading assemblies even if an assembly
* can not be loaded in the new AppDomain. */
return aAssemblies;
}
}
private Assembly OnReflectionOnlyAssemblyResolve(object sender, ResolveEventArgs e)
{
// http://blogs.msdn.com/b/junfeng/archive/2004/08/24/219691.aspx
System.Diagnostics.Debug.WriteLine(e.Name);
AssemblyName name = new AssemblyName(e.Name);
string sAsmToCheck = Path.GetDirectoryName(_sRootAsmDir) + "\\" + name.Name + ".dll";
return File.Exists(sAsmToCheck)
? Assembly.ReflectionOnlyLoadFrom(sAsmToCheck)
: Assembly.ReflectionOnlyLoad(e.Name);
}
}
}
}
Now in my bootstrapper I override the SelectAssemblies method as follows:
...
protected override IEnumerable SelectAssemblies()
{
string sAddinPath = GetAbsolutePath(ADDIN_PATH);
FileCheckList list = new FileCheckList(sAddinPath);
// check only DLL files which were added or changed since last check
SeparateAppDomainAssemblyLoader loader = new SeparateAppDomainAssemblyLoader();
List<string> aAssembliesToRegister = loader.LoadAssemblies(list.GetFiles(null),
sAddinPath, "AssemblyRegisteredWithCM");
string[] aFilesToRegister = (from s in aAssembliesToRegister
select Path.Combine(sAddinPath, s.Substring(0, s.IndexOf(',')) + ".dll")).ToArray();
// update checklist
foreach (string sFile in aFilesToRegister) list.SetCheck(sFile, true);
list.UncheckAllNull();
list.Save();
// register required files
return (new[]
{
Assembly.GetExecutingAssembly(),
}).Union((from s in list.GetFiles(true)
select Assembly.LoadFrom(s))).ToArray();
}
...
As you can see, I am calling the loader not for all the DLL's in my addins path, but only for the ones which a cached files checklist tells me have been added or modified in that folder since the last full scan. This should speed up things a bit and does not require the checklist file to exist: if not found it will be recreated at startup by scanning all the files, if found only added or changed files will be scanned again (I use a CRC to detect changes). So I get the addins folder, create a files checklist for that folder, get from it a list of new or changed files, and pass it to the assemblies loader. This returns only the names of the DLL files which should be registered (i.e. the ones containing assemblies marked with my attribute); I then update the checklist for the next startup, and register only the required files. This way I can let my addin VM's use window managers and correctly locate the view for each required viewmodel. Somewhat ugly, but working. Thanks again to Leaf, who explained me the working of CM.
It appears the MSDN docs are broken concerning creating an Event Log completely along with a definitions file for messages. I am also lost on how to setup Categories (I have custom numbers in the 3000's for messages).
Can anyone point me to a link or show sample code on how to make this right?
You should start (if you haven't done so already) here:
EventLogInstaller Class (System.Diagnostics)
The sample provided there is the foundation for what you want to do. To sum it up, build a public class inheriting from System.Configuration.Install.Installer in an assembly (could be the same DLL where you have the rest of your application, a separate DLL, or an EXE file), decorate it with the RunInstaller attribute, and add your setup code in the constructor:
using System;
using System.Configuration.Install;
using System.Diagnostics;
using System.ComponentModel;
[RunInstaller(true)]
public class MyEventLogInstaller: Installer
{
private EventLogInstaller myEventLogInstaller;
public MyEventLogInstaller()
{
// Create an instance of an EventLogInstaller.
myEventLogInstaller = new EventLogInstaller();
// Set the source name of the event log.
myEventLogInstaller.Source = "NewLogSource";
// Set the event log that the source writes entries to.
myEventLogInstaller.Log = "MyNewLog";
// Add myEventLogInstaller to the Installer collection.
Installers.Add(myEventLogInstaller);
}
}
When you have your assembly compiled, you may use the InstallUtil tool available through the Visual Studio Command Prompt to run the installer code.
Regarding the message definition file (which includes category definitions), the MSDN documentation for EventLogInstaller.MessageResourceFile mentions that you should create an .mc file, compile it, and add it as a resource to your assembly. Digging around, I found an excellent post which should guide you to the end, here:
C# with .NET - Event Logging (Wayback Machine)