Can anybody help me with explaining this error message please:
system.componentmodel.composition.changerejectedexception
The composition remains unchanged. The changes were rejected because of the following error(s): The composition produced a single composition error.
The root cause is provided below. Review the CompositionException.Errors property for more detailed information.
1) No exports were found that match the constraint:
ContractName Itok.BusinessLogic.Interfaces.IFolderService
RequiredTypeIdentity Itok.BusinessLogic.Interfaces.IFolderService
Resulting in: Cannot set import 'Itok.Web.Photos.Presenters.DefaultPresenter._folderService (ContractName="Itok.BusinessLogic.Interfaces.IFolderService")' on part 'Itok.Web.Photos.Presenters.DefaultPresenter'.
Element: Itok.Web.Photos.Presenters.DefaultPresenter._folderService (ContractName="Itok.BusinessLogic.Interfaces.IFolderService") --> Itok.Web.Photos.Presenters.DefaultPresenter
Here is the IFolderService.cs:
using System;
using System.Collections.Generic;
using Itok.Entities;
namespace Itok.BusinessLogic.Interfaces
{
public interface IFolderService
{
List<Folder> GetFriendsFolders(Int32 AccountID);
void DeleteFolder(Folder folder);
List<Folder> GetFoldersByAccountID(Int32 AccountID);
Folder GetFolderByID(Int64 FolderID);
Int64 SaveFolder(Folder folder);
}
}
And this is the exporting class definition, FolderService.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Itok.BusinessLogic.Interfaces;
using System.ComponentModel.Composition;
using Itok.DataAccess.Interfaces;
using Itok.Common;
using Itok.DataAccess;
using Itok.Interfaces;
using Itok.Entities;
namespace Itok.BusinessLogic
{
[Export(typeof(IFolderService))]
[Export(typeof(ICache))]
public class FolderService : IFolderService
{
[Import]
private IFriendRepository _friendRepository;
[Import]
private IFolderRepository _folderRepository;
[Import]
private ICache _cacheService;
public FolderService()
{
MEFManager.Compose(this);
}
public List<Folder> GetFriendsFolders(Int32 AccountID)
{
List<Friend> friends = _friendRepository.GetFriendsByAccountID(AccountID);
List<Folder> folders = _folderRepository.GetFriendsFolders(friends);
folders.OrderBy(f => f.CreateDate).Reverse();
return folders;
}
public void DeleteFolder(Folder folder)
{
if (_cacheService.Exists(folder.AccountID.ToString()))
{
_cacheService.Delete(folder.AccountID.ToString());
}
_folderRepository.DeleteFolder(folder);
}
public List<Folder> GetFoldersByAccountID(int AccountID)
{
List<Folder> cachedFolders = _cacheService.Get(AccountID.ToString()) as List<Folder>;
if (cachedFolders != null)
{
return cachedFolders;
}
else
{
cachedFolders = _folderRepository.GetFoldersByAccountID(AccountID);
_cacheService.Set(AccountID.ToString(), cachedFolders);
return cachedFolders;
}
}
public Folder GetFolderByID(Int64 FolderID)
{
return _folderRepository.GetFolderByID(FolderID);
}
public Int64 SaveFolder(Folder folder)
{
return _folderRepository.SaveFolder(folder);
}
}
}
I thank you prior to any help for saving my time.
The error message means that MEF is looking for a class that is exported with the interface IFolderService but there isn't one in the container.
To investigate this, firstly check that there is a class that exports that interface and if there is, then look into whether that class being picked up by the container or not and thirdly, if neither of those resolve the issue, look into whether the class that is exported with the interface IFolderService has some other imports that can't be satisfied.
Finally, I found the Solution for the problem. It has got has nothing to do directly with IFolderService that MEF was pointing to. The App has dependencies on a component (FolderService) in the business logic, which in turn is dependent upon an interface ICache, and an implementation wrapper, Cache.cs. ICache, specified by a contract name Itok.Interfaces.ICache, had been exported FOUR times (on just one Import). This was left unnoticed while I was trying to scale the solution. MEF couldn't tell which Export to use. The real problem is that MEF was pointing to a class two levels upper the chain!
Thanks TomDoesCode for looking at the problem, and I hope this will help others who'll get a similar problem.
A long term solution for this problem would be if you have many Exports that will satisfy an Import, you'll probably have two options:
I) Change the [Import] with [ImportMany]. Then during runtime, decide which import to use for the contract. Ask yourself if just picking up the first available, or using one at a time in random.
II) Use [ImportMany] in conjunction with Metadata in order to decide which Import to use.
Related
We are trying to combine the Xamarin code that one is created using Xamarin Form (non XAML) and the other one is purely Xamarin.IOS.
We look at the library of Xamarin.Essential and it looks it doesn't have CoreMotion.CMPedometer (iOS) as we need to count the steps.
Is it possible to run the code within the Xamarin Form (shared) to handle specific OS?
Thanks
Yes, you need to use a Dependency Service.
All of the doco can be found here ... https://learn.microsoft.com/en-us/xamarin/xamarin-forms/app-fundamentals/dependency-service/introduction
An example is shown here in relation to device information (which has been cut down for simplicity reasons)
Firstly, you create an interface in your .NET standard/PCL project (if you're not using shared that is, which is likely the case).
using System;
namespace MyApplication.Interfaces
{
public interface IDeviceInfo
{
String GetDeviceModel();
String GetDeviceVersion();
}
}
Then down in your platform specific project, create a Dependency Service that implements that interface and directs the compiler to recognise the class as a Dependency Service.
using System;
using MyApplication.Interfaces;
using UIKit;
[assembly: Xamarin.Forms.Dependency(typeof(MyApplication.iOS.DeviceInfo))]
Namespace MyApplication.iOS
{
public class DeviceInfo : IDeviceInfo
{
UIDevice _device;
Public DeviceInfo()
{
_device = new UIDevice();
}
public string GetDeviceModel()
{
return _device.Model;
}
public string GetDeviceVersion()
{
return _device.SystemVersion;
}
}
}
Now from your .NET standard/PCL project, you can call the dependency service as required.
var deviceModel = DependencyService.Get<IDeviceInfo>().GetDeviceModel();
The above is specific for iOS which means you'd then need to implement the same concept for Android and UWP (or whatever is applicable).
See if that helps you.
I created a website and would like to have a class to centralize all the code that I use frequently in the entire project, for instance, a method to connect to the database. Question: after I create this class, on the App_Code folder, how can I use it in the aspx.cs pages? I mean, should a reference it? Should I inform add a namespace?
Thanks!
Create the class file as public and you will be able to access the class file at any part of your project.
namespace applicationName
{
public class DataManager
{
public static DataTable GetData(StringBuilder sql)
{
}
}
}
you can access the DataManager from your code.
DataManager.GetData(SQL);
Yes, put your class in a namespace and consider making the class static if possible, that way it can be used in code throughout your project without instantiating the class. This is common for utility classes that pass in objects and do work with them, but do not need the actual utility method to be part of a class instance.
For example:
namespace My.Utilities
{
public class static ConnectionStringHelper
{
public static string GetConnectionString()
{
// Logic here to actually get connection string
return yourConnectionString;
}
}
}
Now, code in your project just needs to reference the My.Utilities namespace and then can use the GetConnectionString() method, like this:
using My.Utilities;
string connString = ConnectionStringHelper.GetConnectionString();
You can do it a number of ways. Technically you can drop the namespace completely and your code becomes a free for all (accessible from anywhere naturally). I prefer to use namespaces personally, but I have seem people just avoid them.
If your class Foo is in Some.Namespace, you can reference it as such:
Way one:
Some.Namespace.Foo foo = new Some.Namespace.Foo()
Way two: Use the "Use" command
If your class is inside of Some.Namespace and you don't want all the junk preceding your class name, you can add:
using Some.Namespace;
to the top of your file.
I may be miss understanding what you are saying. If you are talking about setup, you can make a centralized class that manages everything. This class can be a singliton. For instance:
class MyClass
{
public static MyClas Singliton;
static MyClass()
{
Singliton = new MyClass();
}
public void someFunction()
{
}
}
This will create and manage a single reference to your class so that everything is managed out of there (hence being called a "singleton"). As a result, you can access it by:
MyClass.Singliton.someFunction();
There are ways to protect your singliton instance from being overwritten, but this is the basic idea. If you want to manage stuff out of a single location without recreating classes, singletons are the way!
http://msdn.microsoft.com/en-us/library/ff650316.aspx
If the class is wrapped in a namespace, then yes, you'll need a using statement that matches your namespace. For instance, if your class is wrapped in a namespace like so:
namespace My.Namespace
{
public class Foo
{
//Methods, properties, etc.
}
}
then anywhere you want to use that class you'll need to add
using My.Namespace;
to the top of the files where you want to utilize the class(es) you've defined. Then you can use your class as you would expect:
Foo foo = new Foo(); //for a new instance
Foo.Bar(); //for a static method
This is, of course, assuming that the class is in the same assembly and you don't want to mess with adding it to the GAC.
Alternatively, if for some reason you don't to use a using statement you can use the fully qualified name of the class:
My.Namespace.Foo foo = new My.Namespace.Foo(); //for a new instance
My.Namespace.Foo.Bar(); //for a static method
This is most useful if you have namespaces that conflict, for instance if you had
namespace My.Namespace
{
public class Foo
{
//Methods, properties, etc.
}
}
somewhere, and
namespace MyOther.Namespace
{
public class Foo
{
//Methods, properties, etc.
}
}
somewhere else, but needed to use them both in the same scope.
I am having a problem in setting my symbols and retrieving them using Fitnesse symbols. I am creating a new class called Carrier which is a simple Java bean which takes a WebDriver object.
My Java implementation for setting symbols looks like this:
public class ColumnFixtureTest extends ColumnFixture{
private WebDriver driver;
public Carrier together(){
driver = new FirefoxDriver();
Carrier c = new Carrier();
c.setMyDriver(driver);
return c;
}
}
My Java implementation for retrieving them looks like this:
public class SymbolsTest extends ColumnFixture{
private Carrier symbolValue;
public boolean check(){
if(symbolValue.getMyDriver()!=null){
return true;
}
return false;
}
}
My carrier object looks like this:
public class Carrier {
WebDriver myDriver;
public WebDriver getMyDriver() {
return myDriver;
}
public void setMyDriver(WebDriver myDriver) {
this.myDriver = myDriver;
}
}
My Fit table looks like this :
!|ColumnFixtureTest|
|=together()|
|comb|
!|SymbolsTest|
|symbolValue=|check?|
|comb|true|
But after running it, I am getting the following error:
comb
Could not parse: com.symbolTest.Carrier#5ed75ed7, expected type: com.symbolTest.Carrier.
My value is getting set properly though as :
comb = com.ebay.srp.symbolTest.Carrier#5ed75ed7
Any help would be appreciated. Stuck with this for a while now :(
I haven't used the Fit tables in a long time now. I suspect that the problem is that the ColumnFixture class cannot move instances of objects back and forth. It may either only work with stock types that can be expressed as strings. But I could be way off on that.
Is there a reason you are using Fit style tables? I would either recommend that you look at Slim, or go to FitLibrary. For WebDriver testing, FitLibrary has SpiderFixture and there are projects already using WebDriver for Slim (Xebium being an option).
I do know this. Passing around object references in a symbol is supported in Slim.
Suppose I have the following simple wrapper of a NativeClassInstance.
public ref class Wrapper
{
private:
NativeClass *_wrapped;
public:
Renderer()
{
_wrapped = new NativeClass();
}
~Renderer()
{
delete _wrapped;
}
operator NativeClass*()
{
return _wrapped;
}
}
Now, I want to create an instance of Wrapper from C# with Wrapper wrapper = new Wrapper() and use it in another native functionalities wrapper that resides in another assembly with Helper.Foo(wrapper) (nothing strange having other functionalities not directly related to the wrapped classes in another assembly, IMO):
// Utilities is in another Assembly
public ref class Helper
{
public:
static Foo(Wrapper ^wrapper)
{
// Do something in native code with wrapper->_wrapped
}
}
The results with the implicit user conversion is:
candidate function(s) not accessible
If I make _wrapped public it is:
cannot access private member declared in class ...
Now, I've learnt that native type visibility is private outside of the assembly. So, how I'm supposed to use the wrapped entity in native code outside the assembly it's defined? I've read of make_public but you can't use with template types so it seems very limiting in the general case. Am I missing something? Is there a more correct solution?
I haven't been able to successfully expose native types using make_public, however a solution I have used is to put NativeClass in its own native DLL and then a) reference the native DLL from both assemblies; and b) pass the pointer to the native class around as an IntPtr.
Under the above scenario, instead of having an operator NativeClass* you might use a property such as
property IntPtr WrappedObject {
IntPtr get() { return IntPtr(_wrapped); }
}
You then retrieve NativeObject in you helper assembly by
static void Foo(Wrapper ^wrapper)
{
NativeObject *_wrapped
= static_cast<NativeObject*>(wrapper->WrappedObject.ToPointer());
// ... do something ...
}
If you use make_public, your solution of making _wrapped public should work (it would obviously be best to make a public accessor instead). Regarding your comment "I've read of make_public but you can't use with template types so it seems very limiting in the general case." I agree--read here for the workaround I used:
http://social.msdn.microsoft.com/Forums/en-US/vclanguage/thread/b43cca63-b0bf-451e-b8fe-74e9c618b8c4/
More related info:
Best workaround for compiler error C2158: make_public does not support native template types
Good luck!
I have this small app that loads plugin type components that other users can freely upload to the server. But I don't want the users to be able to access other users files. I need to set the access of each plugin component to a restricted access.
I tried to set the access inside the plugin classes base class but even then the loaded plugin classes seem to have full file access.
I can't set the permission with a attribute because the path changes depending on who loads the page.
Here is a code snippest:
public abstract class PluginBase<T>
{
public PluginBase
{
PermissionSet ps = new PermissionSet(System.Security.Permissions.PermissionState.None);
ps.AddPermission(new System.Security.Permissions.FileIOPermission(System.Security.Permissions.FileIOPermissionAccess.PathDiscovery | System.Security.Permissions.FileIOPermissionAccess.Read, HttpContext.Current.Server.MapPath("/app_data/www_somesite_com")));
ps.PermitOnly();
}
}
public class SomePlugin : PluginBase<SomePlugin>
{
public SomePlugin
{
File.WriteAllText("c:\test.txt", "This should not be possible, but it is.. why?");
}
}
Many thanks in advance!
The solution is actually quite simple, as you can implement your own attribute (which allows you to resolve the allowed path programmatically instead of having to use a constant for the decorator attribute).
using System.Security;
using System.Security.Permissions;
public sealed class CustomFileIOPermission : CodeAccessSecurityAttribute
{
public CustomFileIOPermission(SecurityAction action)
: base(action)
{
}
public override IPermission CreatePermission()
{
// You can use your `HttpContext` or similar at this point to resolve the path
string allowedPath = #"D:\test";
return new FileIOPermission(FileIOPermissionAccess.Write, allowedPath);
}
}
The class above will enable use of [CustomFileIOPermission(SecurityAction.PermitOnly)] and will effectively protect files elsewhere.