Develop Reference

C# Interface Inheritance override

I confused about a base interface property hiding, what is still needed in the implemented class, can somebody tell me why?
The goal will be the 'EndClass' only hide/override the 'IClassValue Value', and not need to implement the already hide 'IBaseClassValue Value'.
Thanks!
public interface IBaseClassValue { }
public interface IClassValue : IBaseClassValue { }
public class ClassValue : IClassValue { }
//-----------------------------------------
public interface IEndClassBase
{
IBaseClassValue Value { get; set; }
}
public interface IEndClassBaseChild : IEndClassBase
{
new IClassValue Value { get; set; }
}
//-----------------------------------------
public abstract class EndClassAbs<TValue>
{
TValue Value { get; set; }
}
public class EndClass : EndClassAbs<ClassValue>, IEndClassBaseChild
{
public new IClassValue Value { get; set; }
//IBaseClassValue IEndClassBase.Value { get; set; } //-> Why need here the base member while already hide in the 'IEndClassBaseChild' interface
}

If I use somekind of shadow class '_EndClass' then inherit from it, the 'EndClass' could hide/override the 'ClassValue'. I still don't know why this can not do in one step.
public class _EndClass : EndClassAbs<ClassValue>, IEndClassBase
{
public new IBaseClassValue Value { get; set; }
}
public class EndClass : _EndClass, IEndClassBaseChild
{
public new IClassValue Value { get; set; }
}

How do I create a generic List using abstract class?

I have a Json class "GetAllDevices()". My JSON response consists of an Array/List of objects, where each object has the below common properties.
public class GetAllDevices
{
[JsonProperty("_id")]
public string Id { get; set; }
[JsonProperty("name")]
public string Name { get; set; }
[JsonProperty("type")]
public string Type { get; set; }
[JsonProperty("actions")]
public Action[] Actions { get; set; }
public class Action
{
public string _id { get; set; }
public Action_Def action_def { get; set; }
}
public class Action_Def
{
public string _id { get; set; }
public string name { get; set; }
}
}
I want to create 2 generic lists containing all the above properties based on its "type".
lstfoo1 List contains all the properties(_id, name type and actions) where type="foo1". Similarly, lstfoo2 is a List which contains the above properties where type="foo2".
What I have done so far:
string strJson=getJSON();
Foo1 lstfoo1=new Foo1();
Foo2 lstfoo2=new Foo2();
List<Foo1> foo1list= lstfoo1.GetDeviceData(strJson);
List<Foo2> foo2list = lstfoo2.GetDeviceData(strJson);
public class AllFoo1: GetAllDevices
{
}
public class AllFoo2: GetAllDevices
{
}
public abstract class HomeDevices<T>
{
public string type { get; set; }
public string _id { get; set; }
public List<AllFoo1> lstfoo1{ get; set; }
public List<AllFoo2> lstfoo2{ get; set; }
public abstract List<T> GetDeviceData(string jsonResult);
}
public class Foo1: HomeDevices<AllFoo1>
{
public Foo1()
{
type = "foo1";
}
public override List<AllFoo1> GetDeviceData(string jsonResult)
{
var lst =Newtonsoft.Json.JsonConvert.DeserializeObject<List<AllFoo1>>(jsonResult);
var lst1 = lst.Where(x => x.Type.Equals(type)).ToList();
return lst1;
}
}
public class Foo2: HomeDevices<AllFoo2>
{
public Foo2()
{
type = "foo2";
}
public override List<AllFoo2> GetDeviceData(string jsonResult)
{
var lst = Newtonsoft.Json.JsonConvert.DeserializeObject<List<AllFoo2>>(jsonResult);
var lst1 = lst.Where(x => x.Type.Equals(type)).ToList();
return lst1;
}
}
My question is, is there an easier way to do this using abstract classes? Can I directly convert my "GetAllDevices" class into an abstract class and inherit it and deserialize into it and create a generic list?

This should help, if I understand your problem correctly. Let me know if you have questions or it doesn't work as you need. I put this together really quickly without testing.
The way the Type property is defined could be improved but I left it as you had it.
public class MyApplication
{
public void DoWork()
{
string json = getJSON();
DeviceTypeOne foo1 = new DeviceTypeOne();
DeviceTypeTwo foo2 = new DeviceTypeTwo();
IList<DeviceTypeOne> foo1Results = foo1.GetDeviceData(json); // calls GetDeviceData extension method
IList<DeviceTypeTwo> foo2Results = foo2.GetDeviceData(json); // calls GetDeviceData extension method
}
}
// implemented GetDeviceData as extension method of DeviceBase, instead of the abstract method within DeviceBase,
// it's slightly cleaner than the abstract method
public static class DeviceExtensions
{
public static IList<T> GetDeviceData<T>(this T device, string jsonResult) where T : DeviceBase
{
IEnumerable<T> deviceDataList = JsonConvert.DeserializeObject<IEnumerable<T>>(jsonResult);
IEnumerable<T> resultList = deviceDataList.Where(x => x.Type.Equals(typeof(T).Name));
return resultList.ToList();
}
}
// abstract base class only used to house common properties and control Type assignment
public abstract class DeviceBase : IDeviceData
{
protected DeviceBase(string type)
{
if(string.IsNullOrEmpty(type)) { throw new ArgumentNullException(nameof(type));}
Type = type; // type's value can only be set by classes that inherit and must be set at construction time
}
[JsonProperty("_id")]
public string Id { get; set; }
[JsonProperty("name")]
public string Name { get; set; }
[JsonProperty("type")]
public string Type { get; private set;}
[JsonProperty("actions")]
public DeviceAction[] Actions { get; set; }
}
public class DeviceTypeOne : DeviceBase
{
public DeviceTypeOne() : base(nameof(DeviceTypeOne))
{
}
}
public class DeviceTypeTwo : DeviceBase
{
public DeviceTypeTwo() : base(nameof(DeviceTypeTwo))
{
}
}
// implemented GetAllDevices class as IDeviceData interface
public interface IDeviceData
{
string Id { get; set; }
string Name { get; set; }
string Type { get; }
DeviceAction[] Actions { get; set; }
}
// renamed and relocated class Action to DeviceAction
public class DeviceAction
{
public string Id { get; set; }
public DeviceActionDefinition DeviceActionDefinition { get; set; }
}
// renamed and relocated Action_Def to DeviceActionDefinition
public class DeviceActionDefinition
{
public string Id { get; set; }
public string Name { get; set; }
}

It should be simple enough to move the implementation of method GetDeviceData() to the base class.
For this to work, you will need to add a constraint on T so the compiler knows a bit more about the base type. You will also need to implement a constructor to populate the concrete type's type string you use around. This is a necessary measure to ensure the value is always populated as it is used for comparison in the method in question:
public abstract class HomeDevices<T> where T: GetAllDevices
{
public HomeDevices(string concreteType)
{
type = concreteType;
}
public string type { get; set; }
public string _id { get; set; }
public List<AllFoo1> lstfoo1 { get; set; }
public List<AllFoo2> lstfoo2 { get; set; }
//This method is now generic and works for both.
public List<T> GetDeviceData(string jsonResult)
{
var lst = Newtonsoft.Json.JsonConvert.DeserializeObject<List<T>>(jsonResult);
var lst1 = lst.Where(x => x.Type.Equals(type)).ToList();
return lst1;
}
}
I hope that helps.

Store/retrieve child-parent relationship with JsonConverter

I have a JSON structure (including POCO classes) with child-objects arrays like this:
"Object": [
{
"Name": "TestA",
"ChildObjects": [
{
"Name": "TestB"
"ChildObjects": [
{
"Name": "TestC"
...
}
]
}
]
When deserializing, I would like to keep a reference to the parent
object I've just created.
But I must get this reference before populating the child-object.(On the moment that I populate the child-object I must have the parent-object structure/reference accessible).
I've tried using a custom JsonConverter, but
I could not find a way to store or retrieve this relationship.

Rather than defining this as a serialization problem (how to serialize and deserialize a back-reference to a parent), it might make sense to define this as a class design problem, namely
Given a hierarchy of parents and children, how to ensure that child back-references to parents are automatically set correctly when adding them to their parents?
Once the problem is defined in this way and solved, correctness should be assured both during deserialization and during programmatic data creation, since the parent back-reference would never need to be serialized or deserialized.
One way to accomplish this would be to define a custom subclass of Collection<T> that automatically sets and clears parent back references.
First, define the following interface and collection:
public interface IHasParent<TParent> where TParent : class
{
TParent Parent { get; }
void OnParentChanging(TParent newParent);
}
public class ChildCollection<TParent, TChild> : Collection<TChild>
where TChild : IHasParent<TParent>
where TParent : class
{
readonly TParent parent;
public ChildCollection(TParent parent)
{
this.parent = parent;
}
protected override void ClearItems()
{
foreach (var item in this)
{
if (item != null)
item.OnParentChanging(null);
}
base.ClearItems();
}
protected override void InsertItem(int index, TChild item)
{
if (item != null)
item.OnParentChanging(parent);
base.InsertItem(index, item);
}
protected override void RemoveItem(int index)
{
var item = this[index];
if (item != null)
item.OnParentChanging(null);
base.RemoveItem(index);
}
protected override void SetItem(int index, TChild item)
{
var oldItem = this[index];
if (oldItem != null)
oldItem.OnParentChanging(null);
if (item != null)
item.OnParentChanging(parent);
base.SetItem(index, item);
}
}
Then define your MyObject and RootObject types as follows:
public class MyObject : IHasParent<MyObject>
{
readonly ChildCollection<MyObject, MyObject> childObjects;
public MyObject() { this.childObjects = new ChildCollection<MyObject, MyObject>(this); }
public string Name { get; set; }
public IList<MyObject> ChildObjects { get { return childObjects; } }
#region IHasParent<MyObject> Members
[JsonIgnore]
public MyObject Parent { get; private set; }
public void OnParentChanging(MyObject newParent)
{
Parent = newParent;
}
#endregion
// Added to suppress serialization of empty ChildObjects collections to JSON.
public bool ShouldSerializeChildObjects() { return childObjects.Count > 0; }
}
public class RootObject
{
public RootObject() { this.Object = new List<MyObject>(); }
public List<MyObject> Object { get; set; }
}
Notes:
The collection IList<MyObject> ChildObjects in MyObject is get-only. Json.NET (and XmlSerializer for that matter) can successfully deserialize a get-only, pre-allocated collection.
The method ShouldSerializeChildObjects() is optional and prevents serialization of empty ChildObjects [] array values.
Since ObservableCollection<T> is itself a subclass of Collection<T>, you could chose it as the base class for ChildCollection<TParent, TChild> if you require notifications when items are added or removed.
The Parent property is marked with [JsonIgnore] to prevent its serialization.
Sample fiddle including some basic unit tests.

For clearer understanding dbc's answer let me simplify it.
Let's take example of setting parent for RootObject's item called MyObject:
{
"Object":[
{
"Name": "TestA"
}
]
}
Define collection:
public class Items : Collection<MyObject>
{
private RootObject Owner;
public Items(RootObject owner)
{
Owner = owner;
}
protected override void InsertItem(int index, MyObject item)
{
item.Parent = Owner;
base.InsertItem(index, item);
}
}
Define MyObject and RootObject:
public class MyObject
{
[JsonIgnore]
public RootObject Parent { get; set; }
public string Name { get; set; }
}
public class RootObject
{
public RootObject() { ChildObjects = new Items(this); }
public Items ChildObjects { get; }
}

You needn't JsonConverter.
You can create POCO classes that represent your json, as given below:
public class OstacolisRuntime
{
public int CodiceOstacolo { get; set; }
public int TipoOstacolo { get; set; }
public int Tipologia { get; set; }
public string Nome { get; set; }
public double PosizioneX { get; set; }
public double PosizioneY { get; set; }
public double PosizioneZ { get; set; }
public double AngoloX { get; set; }
public double AngoloY { get; set; }
public double AngoloZ { get; set; }
public double ScalaX { get; set; }
public double ScalaY { get; set; }
public double ScalaZ { get; set; }
public List<SubOggetto> SubOggettos { get; set; } //sub
}
public class SubOggetto
{
public string Immagine { get; set; }
public int Tipologia { get; set; }
public string Nome { get; set; }
public double PosizioneX { get; set; }
public double PosizioneY { get; set; }
public double PosizioneZ { get; set; }
public double AngoloX { get; set; }
public double AngoloY { get; set; }
public double AngoloZ { get; set; }
public double ScalaX { get; set; }
public double ScalaY { get; set; }
public double ScalaZ { get; set; }
public List<SubOggetto> SubOggettos { get; set; } //recursive relashioship
}
public class RootObject
{
public List<OstacolisRuntime> OstacolisRuntime { get; set; }
}
Deserialize you json:
var o= JsonConvert.DeserializeObject<RootObject>(json);
You can check complete source code

Creating base Attribute class with a generic property 'value'

What I've done is created a base class of 'Attribute' in C#. From there I created other classes which inhert Attribute and add any additional properties as necessary. However when I try to create my observable collection which contains all these various attributes I get an underline here
private ObservableCollection<Attribute> _attributes;
under 'Attribute' saying: Using the generic type 'Attribute< TValue >' requires one type arguments. The reason for the base class of Attribute is so I can create multiple attributes as seen below.
Attribute Class
using System.Collections.Generic;
namespace ExampleTool.Model
{
public class Attribute<TValue>
{
public string Key { get; set; }
public TValue Value { get; set; }
}
public class FloatAttr : Attribute<float>
{
public string Label { get; set; }
private float minValue { get; set; }
private float maxValue { get; set; }
}
public class IntAttr : Attribute<int>
{
public string Label { get; set; }
private float minValue { get; set; }
private float maxValue { get; set; }
}
public class StringAttr : Attribute<string>
{
public string Label { get; set; }
}
public class BoolAttr : Attribute<bool>
{
public string Label { get; set; }
}
public class ListStringAttr : List<string>
{
public string Label { get; set; }
}
}
ViewModel - where error occurs...
using System.Collections.Generic;
using System.Collections.ObjectModel;
using ExampleTool.Model;
using ExampleTool.Helper;
namespace ExampleTool.ViewModel
{
public class AttributeViewModel : ObservableObject
{
private ObservableCollection<Attribute> _attributes;
public ObservableCollection<Attribute> Attributes
{
get { return _attributes; }
set
{
_attributes = value;
NotifyPropertyChanged("Attributes");
}
}
public AttributeViewModel()
{
//hard coded data for testing
Attributes = new ObservableCollection<Attribute>();
FloatAttr floatAttr = new FloatAttr();
Attributes.Add(floatAttr);
IntAttr intAttr = new IntAttr();
Attributes.Add(intAttr);
StringAttr stringAttr = new StringAttr();
Attributes.Add(stringAttr);
BoolAttr boolAttr = new BoolAttr();
Attributes.Add(boolAttr);
ListStringAttr listStringAttr = new ListStringAttr();
Attributes.Add(listStringAttr);
}
}
}
Solution idea #1
- simply remove the property of value from the base class and define it in each sub class.
public class Attribute
{
public string Key { get; set; }
}
public class FloatAttr : Attribute
{
public float Value { get; set; }
public string Label { get; set; }
private float minValue { get; set; }
private float maxValue { get; set; }
}
public class IntAttr : Attribute
{
public int Value { get; set; }
public string Label { get; set; }
private float minValue { get; set; }
private float maxValue { get; set; }
}
public class StringAttr : Attribute
{
public string Value { get; set; }
public string Label { get; set; }
}
public class BoolAttr : Attribute
{
public bool Value { get; set; }
public string Label { get; set; }
}
public class ListStringAttr : Attribute
{
public List<string> Value { get; set; }
public string Label { get; set; }
}

Your base Attribute class is a generic type, then you must add type argument to it's usage. But you can't add just T:
private ObservableCollection<Attribute<T>> _attributes;
because T is not your type parameter. You should add new non-generic base class:
public class AttributeBase
{
public string Key { get; set; }
}
public class Attribute<TValue> : AttributeBase
{
public TValue Value { get; set; }
}
And implement AttributeRetriever like in this question:
public Attribute<T> GetAttribute<T>() where T: DatabaseItem, new()
{
return _attributes.OfType(typeof(Attribute<T>)).FirstOrDefault as Attribute<T>;
}
Good news are that your WPF View can works fine without type parameter because Binding uses reflection. Then if you no need to have an access to your properties in code you no need to implement retriever too.

How do I create a List<Item<T>>

Just trying to get my head around this one. Consider the following code.
public class Setting<T> where T: struct
{
public string Name { get; set; }
public T Value { get; set; }
}
public class SettingsDto
{
public List<Setting<>> Settings{ get; set; }
}
The issue is in the SettingsDto class. My Settings property wants me to specify a type for List>. All I know right now is that T must be a struct. How can I create a list of Settings such that I can add to it later - perhaps at runtime. Is there a way around this ?
Many thanks for all replies.

You can carry over the generic parameter over to SettingsDto:
public class SettingsDto<T> where T : struct
{
public List<Setting<T>> Settings { get; set; }
}

You must to pass T generic type to SettingsDto.
Try this:
public class Setting<T> where T: struct
{
public string Name { get; set; }
public T Value { get; set; }
}
public class SettingsDto<T> where T: struct
{
public List<Setting<T>> Settings { get; set; }
}

You can only do it if all settings have something in common. Consider using an interface like this:
public interface ISetting
{
string Name { get; set; }
}
public class Setting<T> : ISetting
where T : struct
{
public string Name { get; set; }
public T Value { get; set; }
}
public class SettingsDto
{
public List<ISetting> Settings { get; set; }
}
class Program
{
static void Main(string[] args)
{
var set=new SettingsDto();
set.Settings=new List<ISetting>();
set.Settings.Add(new Setting<int>() { Name="Setting1", Value=100 });
set.Settings.Add(new Setting<double>() { Name="Setting2", Value=Math.PI });
set.Settings.Add(new Setting<DateTime>() { Name="Setting3", Value=DateTime.Now });
set.Settings.Add(new Setting<int>() { Name="Setting4", Value=200 });
foreach(var setting in set.Settings.OfType<Setting<int>>())
{
Console.WriteLine("{0}={1}", setting.Name, setting.Value);
}
// Setting1=100
// Setting4=200
}
}

Does it has to be struct? Otherwise You could use
public List<Setting<object>> Settings { get; set; }
and cast it when needed.
If it is not for performance reasons, you could put the struct inside a class.