I am trying to register multiple implementations of the same interface like this :-
**DLL A: Module.cs**
_container.RegisterType<IFoo, Foo1>("Foo1");
**DLL B: Module.cs**
var childContainer = _container.CreateChildContainer(); //childcontainer
childContainer.RegisterType<IFoo, Foo2>("Foo2");
**DLL A: Resolve IFoo for Foo2** (But, resolving IFoo for Foo1 is fine)
var foo2 = container.Resolve<IFoo>("Foo2"); //Error
Note: The container which I receive here is the "childcontainer".
Have checked the hashcode.
Error:
A first chance exception
of type 'System.InvalidOperationException' occurred in
Microsoft.Practices.Unity.dll
Additional information: The current type, IFoo, is an interface and
cannot be constructed. Are you missing a type mapping?
But, it works, if I do the registration of Foo2 in DLL A just after Foo1 i.e. like this :
_container.RegisterType<IFoo, Foo1>("Foo1");
_container.RegisterType<IFoo, Foo2>("Foo2");
Is Registration (Register) and Resolution (Resolve) dependent upon scope & assembly ? I want the 1st approach to work. Any idea ?
I tried the next example and is working for me. Just be carefull with assembly references and namespace includes.
**Dll A
Public Interface Ifoo
End Interface
**Dll B
Public Class Class1
Public Shared function registerOtherType(container AS IUnityContainer) As IUnityContainer
Dim c As IUnityContainer = container.CreateChildContainer
c.RegisterType(of Ifoo, foo2)("2")
Return c
End Function
End Class
Public Class foo2
Implements Ifoo
End Class
**Dll C
Public Class foo
Implements Ifoo
End Class
Sub Main()
'init()
'Dim manager As IClasificationManagement = ServiceLocator.Current.GetInstance(Of IClasificationManagement)()
'manager.SwapDescrition("1", "2")
'Console.WriteLine("Operacion Realizada")
'Console.Read()
Dim container As IUnityContainer = New UnityContainer()
container.RegisterType(Of Ifoo, foo )("1")
dim child As IUnityContainer = Class1.registerOtherType(container)
child.Resolve(of Ifoo)("2")
End Sub
Related
Hi I need to create a class for return the data in WCF service. I followed the web at 5 simple steps to create your first RESTful service. However I get the error for . I searched the web and add the System.Runtime.Serialization.DataContractSerializer, Would someone tell me what should do. I am using VS2015 as the tool to build it. Thanks.
Imports System.Runtime.Serialization
Imports System.Collections.Generic
Imports System.Runtime.Serialization.DataContractSerializer
<DataContract>
Public Class Locations
<DataMember>
Public Property LocationName As String
<DataMember>
Public Property LocationID As Integer
End Class
Could you please share the error details with me?
As you know, we usually use the datacontract to transmit the complex data type which could be recognized by the client-side and server-side. so that the data could be serialized and transmitted normally between different platforms.
For the restful web service in WCF, we need to use the Webhttpbinding build the data channel and add the Webhttpbehavior to the service endpoint.
I have made a demo, wish it is useful to you.
Server-side.
Imports System.Runtime.Serialization
Imports System.ServiceModel
Imports System.ServiceModel.Description
Imports System.ServiceModel.Web
Module Module1
Sub Main()
Dim uri As New Uri("http://localhost:900")
Dim binding As New WebHttpBinding()
binding.CrossDomainScriptAccessEnabled = True
binding.Security.Mode = WebHttpSecurityMode.TransportCredentialOnly
binding.Security.Transport.ClientCredentialType = HttpClientCredentialType.None
Using sh As New ServiceHost(GetType(MyService), uri)
Dim se As ServiceEndpoint = sh.AddServiceEndpoint(GetType(IService), binding, uri)
se.EndpointBehaviors.Add(New WebHttpBehavior())
sh.Open()
Console.WriteLine("Service is ready")
Console.ReadLine()
sh.Close()
End Using
End Sub
<ServiceContract([Namespace]:="mydomain")>
Public Interface IService
<OperationContract>
<WebGet(ResponseFormat:=WebMessageFormat.Json)>
Function SayHello() As List(Of Product)
End Interface
Public Class MyService
Implements IService
Public Function SayHello() As List(Of Product) Implements IService.SayHello
Dim result = New List(Of Product)() From {
New Product With {
.Id = 1,
.Name = "Apple"
},
New Product With {
.Id = 2,
.Name = "Pear"
}
}
Return result
End Function
End Class
<DataContract([Namespace]:="mydomain")>
Public Class Product
<DataMember>
Public Property Id() As Integer
<DataMember>
Public Property Name() As String
End Class
End Module
Client.
$(function(){
$.ajax({
type:"GET",
url:"http://10.157.18.188:900/sayhello",
dataType:"jsonp",
success:function(d){
$.each(d,function(i,o){
console.log(o.Id);
console.log(o.Name);
})
}
})
})
Result.
Here is an official sample
https://learn.microsoft.com/en-us/dotnet/framework/wcf/feature-details/how-to-create-a-basic-wcf-web-http-service
I have a class module in my App_code folder.
Private _connection As MySqlConnection
Private _connStr As String
Public Function Connect(dbName As String) As Boolean
Try
_connStr = "Database=" & dbName & ";" & _
"Data Source=192.16.0.1;" & _
"User Id=user;Password=pass"
_connection = New MySqlConnection(_connStr)
_connection.Open()
_connection.Close()
Return True
Catch ex As Exception
_connection = Nothing
Return False
End Try
Return False
End Function
I usually program in webform apps. Why can't I access this function from my aspx code behind pages? I added the import statement for the class. If i make that function shared I cant have those private variables.
I call the function in my aspx lik so;
If Connect(dbName) then....
That gets me an error "non shared member requires an object reference"
You need to add the keyword "Shared" to the method signature, like so:
Private Shared _connection As MySqlConnection
Private Shared _connStr As String
Public Shared Function Connect(dbName As String) As Boolean
This is because otherwise you have instance class members, not static members. The compiler error message is quite self-explanatory.
if you look at this example works:
Public Shared Function example123(ByVal USER As Integer, ByVal Section As String, ByVal ACTION As String) As Boolean
you assign a function shared so you can see it from outside the class
I hope you work
I'm not sure if this is possible but I would like to associate a class name reference to a shared member method / property / variable. Consider:
Public Class UserParameters
Public Shared Reference As Object
Public Shared Function GetReference() As Object
Return Reference
End Function
End Class
In another part of the program I would like to simply call UserParameters and have it return Reference either by aliasing GetReference or the variable directly.
I am trying to emulate the Application, Request, or Session variable:
Session(0) = Session.Item(0)
Any suggestions would be greatly appreciated.
You can't return an instance member from a static method directly (the static method can't access instance members because it isn't instantiated with the rest of the class, only one copy of a static method exists).
If you need to setup a class in such a way that you can return an instance from a static method you would need to do something similar to the following:
Public Class SampleClass
Private Sub New()
'Do something here
End Sub
Public Shared Function GetSample() As SampleClass
Dim SampleClass As SampleClass
SampleClass = New SampleClass
SampleClass.Sample = "Test"
Return SampleClass
End Function
Private _SampleString As String
Public Property Sample As String
Get
Return _SampleString
End Get
Private Set(ByVal value As String)
_SampleString = value
End Set
End Property
End Class
Public Class SampleClass2
Public Sub New()
'Here you can access the sample class in the manner you expect
Dim Sample As SampleClass = SampleClass.GetSample
'This would output "Test"
Debug.Fail(Sample.Sample)
End Sub
End Class
This method is used in various places in the CLR. Such as the System.Net.WebRequest class. where it is instantiated in this manner in usage:
' Create a request for the URL.
Dim request As WebRequest = WebRequest.Create("http://www.contoso.com/default.html")
I have had several occasions recently to access a specific class several times over a relatively small time frame.
So I've been storing the value of the class in Session and trying to access it on page load, if it's not available creating a new instance and storing that in session.
So instead of constantly replicating the same code for different classes on different pages I'm trying to create an extension method to do this for me.
I want to use it like this
Dim objName as MyClass
objName.SessionSingleton()
So far this is what I have for my extension method:
<Extension()> _
Public Sub SessionSingleton(ByRef ClassObject As Object)
Dim objType As Type = ClassObject.GetType
Dim sessionName As String = objType.FullName
If TypeOf HttpContext.Current.Session(sessionName) Is objType And HttpContext.Current.Session(sessionName) <> "" Then
ClassObject = HttpContext.Current.Session(sessionName)
Else
Dim singleton As Object = New objType???????
HttpContext.Current.Session(sessionName) = singleton
ClassObject = singleton
End If
End Sub
I'm stuck on what to do when I make my new instance of my class (it would have to have a New() sub)
I'm not sure where to go from here... or even if this is the best way to do it.
I figured it out and am posting my code for reference. While digging thru pages about Class/Object Factories (thanks RBarry) I found several references to Activator.CreateInstance() in the System.Reflection Class I came up with this.
Imports Microsoft.VisualBasic
Imports System.Runtime.CompilerServices
Imports System.Reflection
Public Module enviornmentUtilities
<Extension()> _
Public Function SessionSinglton(ByVal objType As Type) As Object
Dim sessionName As String = objType.FullName.ToString
If Not HttpContext.Current.Session(sessionName) Is Nothing Then
HttpContext.Current.Trace.Write(HttpContext.Current.Session(sessionName).ToString)
Return HttpContext.Current.Session(sessionName)
Else
Dim ss = Activator.CreateInstance(objType)
HttpContext.Current.Session(sessionName) = ss
Return ss
End If
End Function
End Module
This will let you create a session based singleton from any class that does not require parameters in the new method (which isn't required for this to work)
To test I made a simple Class:
Public Class HasNew
Public FreshInstance As Boolean = True
Public Sub New()
HttpContext.Current.Trace.Warn("This Class has a new method")
End Sub
Public Sub CheckFreshness()
If FreshInstance Then
HttpContext.Current.Trace.Warn("Fresh HasNew Instance")
FreshInstance = False
Else
HttpContext.Current.Trace.Warn("NotFresh HasNew Instance")
End If
End Sub
Public Shared Function type() As Type
Return GetType(HasNew)
End Function
Public Shared Function SessionSinglton() As HasNew
Return GetType(HasNew).SessionSinglton
End Function
End Class
You'll notice the two Public Shared Methods type() and SessionSinglton which calls the above extension method.
With those two functions added we have three ways to initiate the Session Singlton demonstrated here:
Dim HN As HasNew
HN = HasNew.SessionSinglton
HN.CheckFreshness()
HN = HasNew.type.SessionSinglton
HN.CheckFreshness()
HN = GetType(HasNew).SessionSinglton
HN.CheckFreshness()
The Trace Output for this file is as follows:
This Class has a new method
Fresh HasNew Instance
NotFresh HasNew Instance
NotFresh HasNew Instance
The classes new() method is accessed on the first call to the SessionSinglton method and subsequent calls reflect that the instance is in fact being pulled from memory.
I hope this helps someone else in the future.
If you used generics you could just do New T(). Also your SessionSingleton returns "object" type, requiring casting. I did not test this but it should work.
Imports Microsoft.VisualBasic
Imports System.Runtime.CompilerServices
Imports System.Reflection
Public Module enviornmentUtilities
<Extension()> _
Public Function SessionSinglton(Of T As {Class, New})(ByVal obj As T) As T
Dim sessionName As String = obj.GetType.Name
If Not HttpContext.Current.Session(sessionName) Is Nothing Then
HttpContext.Current.Trace.Write(HttpContext.Current.Session(sessionName).ToString)
Return HttpContext.Current.Session(sessionName)
Else
Dim ss = New T()
HttpContext.Current.Session(sessionName) = ss
Return ss
End If
End Function
End Module
I'm building a decent sized application in ASP.NET/VB.NET with various objects... I've never used interfaces before, and a fellow programmer balked when I mentioned this to him. Can anyone give me a quick overview on how they're used, what they're used for, and why I would use them? Maybe I don't need to use them for this project, but if they would help, I surely would love to try.
Thanks so much!
Once you "get" interfaces, OOP really falls into place. To put it simply, an interface defines a set of public method signatures, you create a class which implements those methods. This allows you generalize functions for any class which implements a particular interface (i.e. classes which have the same methods), even if those classes don't necessarily descend from one another.
Module Module1
Interface ILifeform
ReadOnly Property Name() As String
Sub Speak()
Sub Eat()
End Interface
Class Dog
Implements ILifeform
Public ReadOnly Property Name() As String Implements ILifeform.Name
Get
Return "Doggy!"
End Get
End Property
Public Sub Speak() Implements ILifeform.Speak
Console.WriteLine("Woof!")
End Sub
Public Sub Eat() Implements ILifeform.Eat
Console.WriteLine("Yum, doggy biscuits!")
End Sub
End Class
Class Ninja
Implements ILifeform
Public ReadOnly Property Name() As String Implements ILifeform.Name
Get
Return "Ninja!!"
End Get
End Property
Public Sub Speak() Implements ILifeform.Speak
Console.WriteLine("Ninjas are silent, deadly killers")
End Sub
Public Sub Eat() Implements ILifeform.Eat
Console.WriteLine("Ninjas don't eat, they wail on guitars and kick ass")
End Sub
End Class
Class Monkey
Implements ILifeform
Public ReadOnly Property Name() As String Implements ILifeform.Name
Get
Return "Monkey!!!"
End Get
End Property
Public Sub Speak() Implements ILifeform.Speak
Console.WriteLine("Ook ook")
End Sub
Public Sub Eat() Implements ILifeform.Eat
Console.WriteLine("Bananas!")
End Sub
End Class
Sub Main()
Dim lifeforms As ILifeform() = New ILifeform() {New Dog(), New Ninja(), New Monkey()}
For Each x As ILifeform In lifeforms
HandleLifeform(x)
Next
Console.ReadKey(True)
End Sub
Sub HandleLifeform(ByVal x As ILifeform)
Console.WriteLine("Handling lifeform '{0}'", x.Name)
x.Speak()
x.Eat()
Console.WriteLine()
End Sub
End Module
None of the classes above descend from one another, but my HandleLifeform method is generalized to operate on all of them -- or really any class which implements the ILifeform interface.
Since the basics have already been covered, lets move on to practical examples.
Say I'm going to have a Dictionary that stores String keys and Person objects and I'm going to pass this dictionary (actually, the reference to it) to some methods I have.
Now, my receiving method would look something like
Imports System.Collections.Generic
Public Sub DoSomething(ByVal myDict As Dictionary(Of String, Person))
' Do something with myDict here
End Sub
right?
But what if someone invents some new high performance dictionary class? I have to turn around and change every reference to Dictionary to FastDictionary!
However, if I had coded to the interface in the first place, I wouldn't have this problem:
Imports System.Collections.Generic
Public Sub DoSomething(ByVal myDict As IDictionary(Of String, Person))
' Do something with myDict here
End Sub
Now it takes any dictionary!
Interfaces basically allow you to define a type's contract without specifying its implementation.
The idea is that if you know that a given type implements a certain interface it is guaranteeing that certain methods and properties are members of that type.
So any type that implements the following interface:
Interface ISpinnable
Sub Spin()
End Interface
Would have to implement the Spin method. But the caller of this type that implements ISpinnable does not care about how it is implemented, it just cares that the method is there. Here is a type that implements ISpinnable:
Class Top Implements ISpinnable
Sub Spin()
' do spinning stuff
End Sub
End Class
The benefit to this is that you can create method arguments of type ISpinner and allow the caller of these methods to pass any type to you as long as it implements the interface. Your method is no longer tightly coupled to the concrete type that the caller is using.
An interface is a contract without an implementation. It allows you to define what a type will look like without indicating what the implementation of that type is.
This allows you to have various implementations of an interface, which would suit your particular needs.
A good example is the IComparer(Of T) interface. You can have one implementation that will compare two items based on which is greater, and then another which will return a value based on which is lesser.
Then, you could pass one or the other to the static Sort method on the Array class to sort your items in ascending, or descending order, respectively.
One of the things interfaces can be useful is browsing through the array of objects of different types but which share the same interface.
Can't say for VB, but in C# you can use the handy "is" operator to determine if object's type implements the given interface and it's safe to access methods of that interface by casting. Sorry for C#, but i'll try to put some comments in =))
//we declare 3 different interfaces each requiring to implement one method
interface IProgrammer
{
void WriteCode();
}
interface ITester
{
void FindBugs();
}
interface IWorker
{
void StartShift();
}
// each programmer will be able to start his shift and write code
class Programmer : IWorker, IProgrammer
{
public void StartShift()
{
// ...
}
public void WriteCode()
{
// ...
}
}
// each tester will be able to start his shift and find bugs
class Tester : IWorker, ITester
{
public void StartShift()
{
// ...
}
public void FindBugs()
{
// ...
}
}
//then in code you can rely on objects implementing the interface to
// be able to do tasks interface requires to do
static void Main()
{
IWorker[] workers = new IWorker[3];
workers[0] = new Programmer();
workers[1] = new Tester();
workers[2] = new Tester();
// now we can browse through array of different workers because they all share
// the IWorker interface
foreach(IWorker worker in workers)
{
// All IWorkers can StartShift so we access its methods without casts
worker.StartShift();
if(worker is IProgrammer)
{
// Since that worker also implements IProgrammer
// we cast worker as IProgrammer and access IProgrammer method(s)
(worker as IProgrammer).WriteCode();
}
if(worker is ITester)
{
// Same,
// we cast worker as ITester and access ITester method(s)
// handy! =)
(worker as ITester).FindBugs();
}
}
A classic example is the Data Layer where you use it to support multiple database format. This was actually very useful before ORMappers came into the picture in mainstream programming.
Your interface just tells what type of method and properties your object has, the object itself then has to implement these methods.
IMyDatabase myDb;
switch case myDbFormat {
case "mysql":
myDb = new MyDbMySql();
break;
case "mssql" :
myDb = new MyDbMsSql();
break;
}
myDb.SaveToDatabase(some data)
Ofcourse the myDb classes have to implement the ImyDatabase Interface. I assume you can see how useful this is :).