I have a NavigationModel class which implements site navigation. Internally there is a private implementation of NavigationNode which I want to be able to declare within the NavigationModel but not outside of it. How would I accomplish this? When I do the following:
public class NavigationModel
{
public List<NavigationNode> NavigationNodes { get; set; }
public NavigationModel()
{
}
private class NavigationNode
{
}
}
The property tells me:
Inconsistent accessibility: property type
'List' is less accessible than
property 'NavigationModel.NavigationNodes'
The error is raised because by declaring NavigationModel as public, you create a public interface that is used to access NavigationModel. Part of this interface are the signatures of the public methods or properties. By that, you'd publish class NavigationNode that is supposed to be private - hence the error.
In order to fix this, you could create a public interface that only contains the parts of NavigationNode that you want to publish. If you do not want to publish anything, the interface is empty. The following sample shows the basic components:
Public interface INavigationNode.
Property of type List<INavigationNode>.
Private class NavigationNode that implements the interface.
public interface INavigationNode
{
// Add parts of NavigationNode that you want to publish
}
public class NavigationModel
{
public List<INavigationNode> NavigationNodes { get; set; }
public NavigationModel()
{
}
private class NavigationNode : INavigationNode
{
}
}
NavigationNode needs to be public for this to work properly. Making it public still keeps the declaration internal to the containing class NavigationModel yet classes outside NavigationModel can reference it.
Related
I have an app that uses a set of dll's from a 3rdparty. I am trying to incorporate an updated version of the dll's that have changed some variables and parameters from int to uints. I think I can easily capture base class events in my derived class and re-throw modified events, but I am not sure of an easy way to handle the direct access of the variables in the base class's member class.
The example below shows the original 3rd party implementation. In the latest version, the member variables of ThirdPartyNumberPair are now uint's. I'm looking for a way to intercept the MyNumberPair.x and .y access in my derived container and do the conversion so I don't have to modify SomeMethod - mainly because it is used in many places.
public class ThirdPartyNumberPair
{
public int x{ get; set; };
public int y{ get; set; };
}
public class ThirdPartyContainer
{
public ThirdPartyNumberPair MyNumberPair;
}
public class MyDerivedContainer : ThirdPartyContainer
{
...
}
public class MyClass
{
public MyDerivedContainer myContainer;
public void MyMethod(){
int i = myContainer.MyNumberPair.x;
myContainer.MyNumberPair.y = 3;
}
}
I've tried creating a derived MyThirdPartyNumberPair and hiding the base ThirdPartyNumberPair, but I didn't find any easy way of getting those values to the base ThirdPartyNumberPair member.
I want to access a property of some class of mine, but get compiler error "CS0572 - Cannot reference a type through an expression".
I have the following setup
public interface IHelper {
void DoHelp();
}
public abstract class ClassWithHelperBase<THelper> where THelper : IHelper {
public THelper Helper { get; }
}
public class ClassWithHelper : ClassWithHelperBase<ClassWithHelper.Helper> {
// use a nested class, since there will be n classes deriving from ClassWithHelper and giving each helper a readable name (in this example ClassWithHelperHelper) is ugly
public class Helper : IHelper {
public static void SomeStaticMethod() { }
public void DoHelp() { }
}
}
public class Test {
private ClassWithHelper myClass;
public void DoTest() {
((ClassWithHelperBase<ClassWithHelper.Helper>) myClass).Helper.DoHelp(); // this works, but is ugly
myClass.Helper.DoHelp(); // what I want, but it's not working
//myClass.Helper.SomeStaticMethod(); // funnily IDE supposes static methods here even though the resulting code is invalid, since I am (obviously) not referencing the class type
}
}
The interface is unnecessary for reproduction, I added it for clarity.
Note: I do not want to call a static method, I just added it, to show the IDE mixes up the member and the class qualifier.
Is there a way to access the property Helper of myClass, without casting myClass or renaming the nested class?
Aka: Why can't the compiler distinguish the member and the nested class?
The problems is due to name collision between Helper class (type) and Helper property. Try this
public interface IHelper
{
void DoHelp();
}
public abstract class ClassWithHelperBase<THelper> where THelper : IHelper
{
public THelper Helper { get; set; }
}
public class ClassWithHelper : ClassWithHelperBase<ClassWithHelper.CHelper>
{
// use a nested class, since there will be n classes deriving from ClassWithHelper and giving each helper a readable name (in this example ClassWithHelperHelper) is ugly
public class CHelper : IHelper
{
public static void SomeStaticMethod() {}
public void DoHelp() { }
}
}
public class Test
{
private ClassWithHelper myClass;
public void DoTest() {
myClass.Helper.DoHelp();
ClassWithHelper.CHelper.SomeStaticMethod();
}
}
Here I renamed Helper class to the CHelper, so compiler can now distinguish class and property and thus the line myClass.Helper.DoHelp(); now works without cast.
If a "do not rename nested class" requirement is absolutely mandatory, then the problem may be also solved by renaming the Helper property in the base class to avoid name collision. However, I can't imagine better name for the property.
Unfortunately, for the static method, you can't reference myClass instance. So, you will need reference the whole type.
I've got the following bit of (simplified) code:
public abstract class BaseClass
{
[Dependency]
public IRequiredService RequiredService { get; set; }
protected string RequiredParameter { get; private set; }
public BaseClass(string requiredParameter)
{
this.RequiredParameter = requiredParameter;
}
}
public class DerivedClass : BaseClass
{
public DerivedClass(string requiredParameter) : base(requiredParameter)
{
RequiredService.DoSomething(); //this will fail!
}
}
In other words, I'd like to have access to the Unity-filled RequiredService in the constructor... but that's impossible, since that property hasn't been filled by Unity yet. I COULD add the IRequiredService as a required constructor parameter, but then I'd need to refactor every constructor of every derived class to also include that parameter.
I was wondering if there's a better way.
In short, I'd like to run a bit of code after a class has been constructed and after unity has filled all the class' properties marked with the [Dependency] attribute.
Is there a simple way to do this?
Instead of putting RequiredService.DoSomething(); in the constructor you can put it in a inside a [InjectionMethod] call, this will allow you to reliably know that RequiredService has been populated.
Im not sure if it is possible. I am running into a unique issue dealing with a clients api.
I am needing to extend a class and add a bool property that does not exist in the base class.
below is an example of what I am trying to accomplish.
public class baseClass
{
//.. No Editable Access
}
public class Extended
{
public bool flaggedAsDeleted(this baseClass bc)
{
//Idealy was looking for get; set; but I know that don't work
return true;// Need to know if possible to set property on baseClass or Alternative
}
public void flagAsDeleted(this baseClass bc)
{
flaggedAsDeleted = true;
}
}
public class program
{
public void doit()
{
baseClass bc = new baseClass();
bc.flagAsDeleted();
}
}
If you're trying to actually extend a class, you do it like this:
public class BaseClass
{
//.. No Editable Access
}
public class Extended : BaseClass
{
public bool FlaggedAsDeleted { get; set; }
}
If you're trying to add data to an existing class, you have two options:
Inheritance - as seen above.
Encapsulation - create a new object that holds an instance of the type you're adding to.
C# provides a feature called Extension Methods, which allows you to seemingly add methods to existing classes. However, these are really just syntactic sugar, as you're still constrained to the class's public API.
public class BaseClass
{
public int Value { get; set; }
}
public static class ExtensionMethods
{
public static void Increment(this BaseClass b)
{
b.Value += 1;
}
}
Extension methods do not allow you to add data to an existing class though.
This is not unique. This is a common problem solved using a Design Pattern called decorator.
i have another question open here on SO and after thinking about it, i may be approaching this in the wrong way.
i have 4 classes, that have the same properties and methods.
some of the classes, have their own properties and methods ( not overrides of the existing ones ).
currently i create each class as:
public class ClassOne
{
public ClassOne()
{
}
public int ID {get;set;}
// More properties here
public void Set(){
// Do Stuff to save this
}
// More Methods here
}
cant i create one class that will generate all of the 4 classes?
and in the classes themselfs i only create specific properties/methods for that class?
repeating the code seems very odd to me, im sure there must be a way to do this, just dont know how.
Your situation is one of the main reasons why inheritance was invented. So with that, you can write
public class Base
{
// Properties and methods common to all
}
public class ClassOne : Base
{
// Properties and methods specific to ClassOne
}
public class ClassTwo : Base
{
// Properties and methods specific to ClassTwo
}
public class ClassThree : Base
{
// Properties and methods specific to ClassThree
}
public class ClassFour : Base
{
// Properties and methods specific to ClassFour
}
As requested, more code, using interfaces and abstract classes:
An interface is just a blueprint, defining what properties and methods are required to be compatible with other "BaseClasses"
public interface IBaseClass
{
public int ID {get;set;}
public void Set();
}
Abstract classes can contain code, but can not be instantiated, they are form of starting point for a class, but not a complete class themselves.
public abstract class ABaseClass : IBaseClass
{
public int ID {get;set;}
public void Set(){
// Do Stuff to save
}
}
Each class inherits from the abstract class and can then override and implement whatever it wants, customizing it however is necessary.
public class ClassOne : ABaseClass
{
}
public class ClassTwo : ABaseClass
{
}
public class ClassThree : ABaseClass
{
}
public class ClassFour : ABaseClass
{
}
ps. not entirely sure if my syntax is 100% correct
Could you simply make a base class with your properties and inherit from that class?
Why not use inheritance??
public class ClassOne
{
public ClassOne()
{
}
public virtual int ID {get;set;}
// More properties here
public virtual void Set(){
// Do Stuff to save this
}
// More Methods here }
public class ClassTwo : ClassOne
{
public string ClassTwoString { get; set; }
}
public class ClassThree : ClassOne
{
public string ClassThreeString { get; set; }
}
Can you make them all inherit off of the same class? If so, that sounds ideal.
Barring the possibility of making them inherit, you could write an interface that describes the methods and properties which each of them use. Then you can call each instance of the class through the same interface.
Barring again that possibility, you could write a reflective assignor/accessor. But you shouldn't do that.