i write silverlight program very simple.i use Mef and WCF.
this code is MainPageViewModel class that included Commands and properties.
public List<NoOfStudentsDropDownItem> ListNoOfStudent{get;set;}
public MainPageViewModel()
{
InitializList();
}
private void InitializList()
{
ListNoOfStudent.Add(New NoOfStudentsDropDownItem(){DisplayText="1",NoOfStudent=-1});
ListNoOfStudent.Add(New NoOfStudentsDropDownItem(){DisplayText="5",NoOfStudent=5});
}
this is NoOfStudentsDropDownItem class;
public Class NoOfStudentsDropDownItem
{
public string DisplayText{get;set;}
public int NoofStudent{get;set}
}
this is part of App Class.
private void Application_Startup(object sender,StartupEventArgs e)
{
CompositionInitializer.SatisfyImports(this);
MainPage mainpage=new MainPage();
mainpage.DataContext=MainViewModel;
this.RootVisual=mainpage;
}
[Import]
public MainPageViewModel MainViewModel{get;set;}
i haven't error when commented InitializList method.i dont know cause.
You simply forgot to create the list. You declared a property for it, but it is never assigned so it will still be null when you call Add.
Related
I'm running a C# project on VS2019 with the following code structure:
In the Class1.cs file:
public class Class1
{
public class MyClass2 : Class2
{
...
}
private void RunAlgorithm<T>() where T : Class2, new()
{
T argInstance = new T();
...
}
static void Main(string[] args)
{
RunAlgorithm<MyClass2>();
}
}
In the Class2.cs file:
public class Class2
{
public Class2() { }
public string setParameters { get; set; }
}
I'm getting the following error for the line RunAlgorithm<MyClass2>();
'Class1.MyClass2' must be a non-abstract type with a public
parameterless constructor in order to use it as parameter 'T' in the
generic type or method 'Class1.RunAlgorithm()'
even if I change it to Public, the error persists
Well, minimally, it'll have to be protected so that MyClass can access it..
https://dotnetfiddle.net/XFeEdQ
public class Class1
{
class MyClass2 : Class2
{
}
private void RunAlgorithm<T>() where T : Class2, new()
{
T argInstance = new T();
}
public static void Main(string[] args)
{
new Class1().RunAlgorithm<MyClass2>();
}
}
public class Class2
{
protected Class2() { }
public string setParameters { get; set; }
}
So your "Class1.MyClass2
must have a public parameterless constructor" message is saying that your MyClass needs a constructor. Mine above has such a constructor even though it's not in the code; in the absence of the developer providing a constructor the compiler provides one that does nothing other than call the base parameterless constructor...
...which leads me to the next point; your MyClass2 extends Class2, and hence Class2's constructor needs to be accessible to it. While Class2's constructor is private, MyClass2's constructor can't call it. Every constructor on c# has to either call another constructor or a base constructor. If you don't specify which, the compiler will insert a call to base() for you, which will fail if the base constructor is inaccessible
For this all to work out you need a public parameterless constructor in MyClass2:
public MyClass2():base(){}
or without the base(compiler will add the base call)
or blank (compiler will add all of it)
and you need something that makes Class2's constructor accessible to MyClass2, ie declaring Class2's constructor as public or protected
Single interface: IDoSomething {...}
Two classes implement that interface:
ClassA : IDoSomething {...}
ClassB : IDoSomething {...}
One class uses any of those classes.
public class DummyClass(IDoSomething doSomething) {...}
code without Autofac:
{
....
IDoSomething myProperty;
if (type == "A")
myProperty = new DummyClass (new ClassA());
else
myProperty = new DummyClass (new ClassB());
myProperty.CallSomeMethod();
....
}
Is it possible to implement something like that using Autofac?
Thanks in advance,
What you are looking for is, as I remember, the Strategy Pattern. You may have N implementations of a single interface. As long you register them all, Autofac or any other DI framework should provide them all.
One of the options would be to create a declaration of the property with private setter or only getter inside Interface then implement that property in each of the class. In the class where you need to select the correct implementation, the constructor should have the parameter IEnumerable<ICommon>.
Autofac or any other DI frameworks should inject all possible implementation. After that, you could spin foreach and search for the desired property.
It may look something like this.
public interface ICommon{
string Identifier{get;}
void commonAction();
}
public class A: ICommon{
public string Identifier { get{return "ClassA";} }
public void commonAction()
{
Console.WriteLine("ClassA");
}
}
public class A: ICommon{
public string Identifier { get{return "ClassB";} }
public void commonAction()
{
Console.WriteLine("ClassA");
}
}
public class Action{
private IEnumerable<ICommon> _common;
public Action(IEnumerable<ICommon> common){
_common = common;
}
public void SelectorMethod(){
foreach(var classes in _common){
if(classes.Identifier == "ClassA"){
classes.commonAction();
}
}
}
}
When I implement the ICommand interface, the following methods are created
#region ICommand Members
public bool CanExecute(object parameter)
{
}
public event EventHandler CanExecuteChanged;
public void Execute(object parameter)
{
}
#endregion
The interesting part is
public void Execute(object parameter)
{
}
Simply because it indicates that it expects 1 parameter. What if I don't need to pass a parameter? In my ViewModel I have the following code
public class DownloadViewModel : BaseViewModel
{
public ICommand BrowseForFile { get; set; }
public string File { get; set; }
public DownloadViewModel()
{
BrowseForFile = new RelayCommand(new Action<object>(OpenDialog));
}
private void OpenDialog(object o)
{
var dialog = new System.Windows.Forms.FolderBrowserDialog();
System.Windows.Forms.DialogResult result = dialog.ShowDialog();
File = dialog.SelectedPath;
}
}
The OpenDialog method does not require the parameter but it appears as if I have to just so I can satisfy the Interface.
Am I doing this right or have I missed the point?
Yes, ICommand always needs an object and RelayCommand too. If you don't need it, you pass null and don't use it in your method, which is ugly.
I would use Prism's DelegateCommand instead. This exists in a non-generic version, which doesn't take parameters:
Command = new DelegateCommand(DoSomething);
CommandWithParameter = new DelegateCommand<int>(DoSOmethingWithInt);
Its in the PRISM assembly, which you have to download and reference.
using Microsoft.Practices.Prism;
PRISM
Alternatively, use the MVVMLight toolkit, which provides a command class which does basically the same thing. There is no point in using MVVM without a MVVM framework anyway. I can recommend PRISM, also for it's basic stuff like the DelegateCommand or the EventAggregator.
The fact that Execute takes a parameter is irrelevant to the method from your ViewModel. The only thing that affects what parameters OpenDialog needs is your implementation of ICommand.
If your implementation is, for example:
public class MyRandomCommand : ICommand
{
private readonly Action _action;
public MyRandomCommand(Action action)
{
_action = action;
}
public void Execute(object parameter)
{
_action();
}
...
}
Then no parameters will be required for your OpenDialog method, as you can create a command as follows:
public ICommand Command { get { return new MyRandomCommand(OpenDialog); } }
You can, however, require any signature you like for the method you are passing to your command.
The most common, off-the-shelf implementations of RelayCommand can take methods with either 0 or 1 parameter and will be called from Execute appropriately.
I'm building a small Nancy web project.
In a method of one of my classes (not a nancy module), I would like to basically do:
var myThing = TinyIoC.TinyIoCContainer.Current.Resolve<IMyThing>();
However, there is only one registration in .Current (non public members, _RegisteredTypes) which is:
TinyIoC.TinyIoCContainer.TypeRegistration
Naturally, in my above code, I'm getting:
Unable to resolve type: My.Namespace.IMyThing
So, I guess I'm not getting the same container registered in my bootstrapper?
Is there a way to get at it?
EDIT
To flesh out a bit more of what I'm trying to do:
Basically, my url structure looks something like:
/{myType}/{myMethod}
So, the idea being, going to: /customer/ShowAllWithTheNameAlex would load the Customer service, and execute the showAllWithTheNameAlex method
How I do this is:
public interface IService
{
void DoSomething();
IEnumerable<string> GetSomeThings();
}
I then have an abstract base class, with a method GetService that returns the service.
It's here that i'm trying to use the TinyIoC.TinyIoCContainer.Current.Resolve();
In this case, it would be TinyIoC.TinyIoCContainer.Current.Resolve("typeName");
public abstract class Service : IService
{
abstract void DoSomething();
abstract IEnumerable<string> GetSomeThings();
public static IService GetService(string type)
{
//currently, i'm doing this with reflection....
}
}
Here's my implementation of the service.
public class CustomerService : Service
{
public void DoSomething()
{
//do stuff
}
public IEnumerable<string> GetSomeThings()
{
//return stuff
}
public IEnumerable<Customer> ShowAllWithTheNameAlex()
{
//return
}
}
Finally, I have my Nancy Module, that looks like:
public class MyModule : NancyModule
{
public MyModule()
{
Get["/{typeName}/{methodName}"] = p => ExecuteMethod(p.typeName, p.methodName);
}
private dynamic ExecuteMethod(string typeName, string methodName)
{
var service = Service.GetService(typeName);
var result = service.GetType().GetMethod(methodName).Invoke(service, null);
//do stuff
return result; //or whatever
}
}
#alexjamesbrown - The short answer is, you don't. Nancy was specifically designed so that you did not deal with the container directly. You mention that the class, that you want to take a dependency on IMyThing, is not a NancyModule. Well this is not an issue, as long as one of your modules has a reference to it, then those dependencies can also have their own dependencies that will be satisfied at runtime.
public interface IGreetingMessageService
{
string GetMessage();
}
public class GreetingMessageService: IGreetingMessageService
{
public string GetMessage()
{
return "Hi!";
}
}
public interface IGreeter
{
string Greet();
}
public class Greeter
{
private readonly IGreetingMessageService service;
public Greeter(IGreetingMessageService service)
{
this.service = service;
}
public string Greet()
{
return this.service.GetMessage();
}
}
public class GreetingsModule : NancyModule
{
public GreetingModule(IGreeter greeter)
{
Get["/"] = x => greeter.Greet();
}
}
The above will work just fine and Greeter will have it's dependency on IGreetingMessageService satisfied at runtime
I have had a very similar issue, needing to "share" the container. The reason this is an issue is that my program runs as a service using Nancy self hosting to provide a REST API. My modules have dependencies which are injected by Nancy itself, but the other parts of the app which are not referenced from modules also need dependencies injected.
Multiple containers are not a sensible option here (or anywhere really), I need to share the container between Nancy and the rest of the app.
I simply did the following
(I'm using Autofac but I suspect that TinyIoC in similar)
public class Bootstrapper : AutofacNancyBootstrapper
{
private static readonly Lazy<ILifetimeScope> container = new Lazy<ILifetimeScope>(RegisterTypes);
public static ILifetimeScope Container => container.Value;
protected override ILifetimeScope GetApplicationContainer()
{
return container.Value;
}
// Create container and register my types
private static ILifetimeScope RegisterTypes()
{
var builder = new ContainerBuilder();
// Register all my own types.....
return builder.Build();
}
}
Then, in my main code, I can use the container myself
public class Program
{
public static void Main(string[] args)
{
// Resolve main service with all its dependencies
var service = Bootstrapper.Container.Resolve<Service>();
service.Run();
}
}
As my NancyHost is within the Service, the container is constructed (once) upon its first use in main, this static is then used when Nancy gets round to creating the Bootstrapper itself.
In an ideal world, I wouldn't really want a globally accessible container, normally it would be local to the main function.
In this particular case "not dealing with the container directly" is highly problematic:
public interface IFoo {}
public class Foo : IFoo { public Foo(string bar) {} }
Assume IFoo already is a constructor dependency of a Nancy module.
Note the Foo constructor's string dependency. I need to communicate to the container to use that constructor for an IFoo singleton, when encountered as a Nancy module dependency. I need to register that on the TinyIoC instance NancyFx uses, and pass in the actual value of bar.
I'd like to add one additional method for each service operation in my WCF client proxy code (i.e. the generated class that derives from ClientBase). I have written a Visual Studio extension that has an IOperationContractGenerationExtension implementation, but this interface only seems to expose the ability to modify the service interface, not the ClientBase-derived class.
Is there any way to generate new methods in the proxy client class?
As far as I know, those classes are always partial classes:
public partial class MyWCFServiceClient : ClientBase<IMyWCFService>, IMyWCFService
{
...
}
so you can easily extend them with your own, second file that adds method to the same partial class:
YourOwnFile.cs
public partial class MyWCFServiceClient
{
public void NewMethod1()
{
}
public void NewMethod2()
{
}
}
I got around this by generating a wrapper class for the ClientBase-derived class during the import process. I actually first tried generating an additional partial class with the same name as the client class, but that caused the rest of the code generation to stop working properly.
So my final generated code looks something like:
(generated by the built-in WCF proxy generator):
public interface ServiceReference1
{
IAsyncResult BeginWebMethod1(AsyncCallback callback, object asyncState);
void EndWebMethod1(IAsyncResult result);
IAsyncResult BeginWebMethod2(AsyncCallback callback, object asyncState);
void EndWebMethod2(IAsyncResult result);
// ...
}
public class ServiceReference1Client
{
public event EventHandler<AsyncCompletedEventArgs> WebMethod1Completed;
public event EventHandler<AsyncCompletedEventArgs> WebMethod2Completed;
public void WebMethod1Async() { /* ... */ }
public void WebMethod2Async() { /* ... */ }
// ...
}
(generated by my custom IOperationContractGenerationExtension):
public class ServiceReference1Wrapper
{
private ServiceReference1Client _client;
public ServiceReference1Wrapper(ServiceReference1Client client)
{
_client = client;
}
public IObservable<AsyncCompletedEventArgs> WebMethod1()
{
_client.WebMethod1Async();
// ...
}
public IObservable<AsyncCompletedEventArgs> WebMethod2()
{
_client.WebMethod2Async();
// ...
}
// ...
}
Note: I'm using Silverlight, so that's why everything is async.