Accessing a Property of Derived Class from the Base Class in C#

Accessing a property of derived class from the base class in C#

Certainly you can downcast, like so:

for (int i = 0; i < MyList.Count; i++)
{
    if (MyList[i] is ClassA)
    {
        var a = ((ClassA)MyList[i]).PropertyA;
        // do stuff with a
    }

    if (MyList[i] is ClassB)
    {
        var b = ((ClassB)MyList[i]).PropertyB;
        // do stuff with b
    }
}

... However, you should take another look at what you're trying to accomplish. If you have common code that needs to get to properties of ClassA and ClassB, then you may be better off wrapping access to those properties up into a shared, virtual property or method in the ancestor class.

Something like:

public class BaseClass
{
    public virtual void DoStuff() { }
}

public class ClassA : BaseClass
{
    public object PropertyA { get; set; }

    public override void DoStuff() 
    {
        // do stuff with PropertyA 
    }
}

public class ClassB : BaseClass
{
    public object PropertyB { get; set; }

    public override void DoStuff() 
    {
        // do stuff with PropertyB
    }
}

how to access properties in derived class stored in a list of the base class

You will have to use explicit casting, the code would look like this,

// This is the Child Class which derives from class Base.

Child c = new Child();

//UpCast can be done implicitly without any issues

Base b = c;

//Explicit conversion is required to cast the object back to derived.

Child c1 = (Child) b;

Now , since this is runtime operation, you will not get an error in case of incorrect casting, hence always make a check before casting. you can use "is" or "as" keyword, Below are the links that will give you more details.

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/as

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/is

Hope this helps

Better way of passing properties of base class to derived class?

This is the proper implementation:

public class TheBase
{
    public int One { get; set; }
    public int Two { get; set; }
    public int Three { get; set; }
    public TheBase(int one, int two, int three)
    {
        One = one;
        Two = two;
        Three = three;
    }
    public TheBase(TheBase theBase)
    {
        One = theBase.One;
        Two = theBase.Two;
        Three = theBase.Three;
    }
}
public class Derived : TheBase
{
    public int Four { get; set; }
    public int Five { get; set; }
    public Derived(TheBase theBase, int four, int five) : base(theBase)
    {
        Four = four;
        Five = five;
    }
    public Derived(int one, int two, int three, int four, int five) : base(one, two, three)
    {
        Four = four;
        Five = five;
    }
}

How to use a derived property on a base class?

Hiding a member with the new keyword should generally be avoided. Instead make the base class' property virtual and override it in the descending class. The MyBaseMethod will automatically use this overridden property in inheriting classes.

public class MyBase
{
    public virtual string MyProperty { get { return "Base"; } }

    public string MyBaseMethod()
    {
        return MyProperty;
    }
}

public class MyInherited : MyBase
{
    public override string MyProperty { get { return "Inherited"; } }
}

---

var inherited = new MyInherited();
Console.WriteLine(inherited.MyBaseMethod()); // ==> "Inherited"

See this interesting post related to the new keyword: Why do we need the new keyword and why is the default behavior to hide and not override?

Get properties from derived class in base class

If both classes are in the same assembly, you can try this:

Assembly
    .GetAssembly(typeof(BaseClass))
    .GetTypes()
    .Where(t => t.IsSubclassOf(typeof(BaseClass))
    .SelectMany(t => t.GetProperties());

This will give you all the properties of all the subclasses of BaseClass.

C# Use base class property value in a derived class property override

Use base.AnimalId

public class Animal
{
    private int _animalId;

    public virtual int AnimalId
    {
        get { return _animalId; }
    }
}

public class Dog : Animal
{
    public override int AnimalId
    {
        get 
        { 
            if (Request.Params["New_Animal"] == "true")
                return -1;
            else
                return base.AnimalId;
        }
    }
}

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