Calling a constructor of a unknowed at compile time class

Question

This is my situation: I have classes represeting properties:

public abstract class RootProperty { 
    public int Id {get; set;}
}
public class AProperty {}
public class BProperty {}

and let there be a looot of these:

public class ZProperty {}

And a value for each of this properties,

public abstract class RootValue {
    public RootProperty Property {get;set;}
}
public class AValue : RootValue {
    public AValue(AProperty) { ... }
    public string Value {get; set;} 
}
public class ZValue : RootValue {
    public ZValue(ZProperty) { ... }
    public sometipe Value {get;set;} }

In fact, each class is representing a type of property than a thing must have. So if i want to say that a property is defined by a string wich must have value in a given domain i say:

public class DomainProperty {
    public ICollection<string> Domain {get; set;}
}
public class DomainValue {
    public DomainValue(DomainProperty) {...}
    public string Value
    {
        set { 
            if (!this.Property.Domain.Any(d=>d==value)) {
                throw new Exceptin("Value out of range!");
            }
        }
    }
}

So I can dogs can be small or big, and mine is big.

DomainProperty DogsSize = new DomainProperty { Domain= ["big","small"] }
DomainValue MyDogSize = new DomainValue(color) { Value = "big" }

Using this, I can define properties on numeric ranges with max and min value, etc. Okey, the first question here is: can you think some other solution for this problem of coustomizable types of properties?

Now, the questio that bring me to post here: The previous logic is on the server side, and its reciving from the client side a list of abstract dtos:

public abstract class RootDto { public int PropertyId { get; set; } }
public class ADto : RootDto { public string Value { get; set; } }
public class BDto: RootDto { public bool Value { get; set; } }
public class ZDto : RootDto { public someothertype Value { get; set; } }

With RootDto PropertyId I can find the original RootProperty. I want to create a new instance of ?Value, and set the value to ?Dto.Value. Now I have this on a lot of casts:

List<RootDto> listDto;
foreach(dto in listDtio) {
    if (someDto is ADto) {
        ADto castedDto = (ADto) dto;
        AProperty dtoProperty = (AProperty) Repository.findRootProperty(dto.PropertyId);
        AValue valueForDto = new AValue(dtoProperty);
        valueForDto.Value = castedDto.Value;
    }
    if ...(B.....Z)
}

That works, but a loot of lines of repetive code if you have say, 15 posible property classes. I have investigated Reflection and dynamic types but found nothing, can you help me? Thanks for your time, I hope I gave a nice explanation.

Answer 1

Your code is very confusing, so, my answer code is not the very best as well, but if you understand your code, you can understand the answer.

The first approach I would try is generics:

First make some abstract value get, set in the root classes:

public abstract class RootValue 
{
    public RootProperty Property {get;set;}
    public abstract object ValueInRoot {get; set;}
}

public abstract class RootDto 
{ 
    public int PropertyId {get; set; } 
    public abstract object ValueInRoot {get; set; }
}

Since you create new AProperty in your last method, I believe it also inherits RootProperty, so, RootProperty should follow the above idea as well. But I believe you will find out that Property class might not be needed. (See comments in ValueClass) Id suggest RootProperty had a CreateValue method:

public abstract class RootProperty 
{ 
    public int Id {get; set;}

    public abstract RootValue CreateValue();
}

Where you have AProperty through ZProperty, use a single class declaration like this. It's a generic class, takes a type parameter (TValue), wich is not known at compile time.

//I really believe the properties are inheriting RootProperty
public class Property<TValue> : RootProperty
{
    public ValueClass<TValue> CreateTypedValue()
    { 
        //Create the new ValueClass<TValue> here;
        //I believe it's the best place to do that.

        //It will know the type and it can be called via the 
        //overriden method below

        //This way you avoid calling the Value contructor in your 
        //final method.
    }

    public override RootValue CreateValue()
    {
        return this.CreateTypedValue();
    }
}

Where you have AValue throug ZValue, use this, overriding that Root value: (Beware, since I don't know how you use the Property here, take a look at the comments in constructor to see the idea)

public class ValueClass<TValue> : RootValue 
{
    //this line is not clear for me....
    public ValueClass(Property<TValue>) 
    { 
        //I believe you should leave the task of creating this ValueClass to the 
        //Property CreateTypedValue() method.

        //See that I added the CreateValue in te property classes,
        //you will see further on why I did that. It solves constructor problem.
    }         

    public TValue Value {get; set;}

    public override object ValueInRoot
    {
        get { return Value; }
        set { Value = (TValue)value; }
    }
}

For the domain:

public class DomainProperty<TValue> 
{
    public ICollection<TValue> Domain {get; set;}
}

public class DomainValue<TValue> 
{
   public DomainValue(DomainProperty<TValue>) {...}
   public TValue Value
    {
        set { 
            //Here I'd use Domain.Contains(value)
            if (!this.Property.Domain.Any(d=>d==value)) 
             {
                 throw new Exceptin("Value out of range!");
             }
         }
   }
 }

For the DTOs, that also overrides the root value:

public class Dto<TValue> : RootDto 
{
    public TValue Value {get; set;} 
    public override object ValueInRoot
    {
        get { return Value; }
        set { Value = (TValue)value; }
    }
}

---

And finally, your assign method on server:

foreach(dto in listDtio) 
{
    //if (someDto is ADto) 
    //{
        //ADto castedDto = (ADto) dto;
        RootProperty dtoProperty = Repository.findRootProperty(dto.PropertyId);

        //here is the way you solve your constructor problem.
        RootValue valueForDto = dtoProperty.CreateValue();

        //and here you assign values without knowing their types,
        //but they will still be typed
        valueForDto.ValueInRoot = dto.ValueInRoot;
    //}
    //if ...(B.....Z)
}

Answer 2

To give a start: I would say that some possible solution is iterate in constructors of all classes extending from RootValue, find some with a XProperty argument, call it, and asign Value dynamically