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c#genericsinheritance
CSCoder
CSCoder

Reputation: 150

Specify generic type based on sub class C#

Is it possible in C# to define a generic method in a base class and then have the type be defined based on what subclass is calling it.

abstract class BaseClass
{
    void SomeMethod<T>()
    {
        ...
    }
}

class SubClass1 : BaseClass
{
    ...
}

class SubClass2 : BaseClass
{
    ...
}

Now if i call SomeMethod from an instance of SubClass1 I want it to use one type (let's say string) and if i call it from an instance of SubClass2 I want it to use a different type (let's say int). So...

BaseClass instance1 = new SubClass1();
BaseClass instance2 = new SubClass2();
instance1.SomeMethod() //this should call SomeMethod<string>()
instance2.SomeMethod() //this should call SomeMethod<int>()

Is this possible?

Update

I would like to have one BaseClass variable be assigned an instance of either SubClass1 or SubClass2:

for (int i = 0; i < numSubClasses; i++)
{
    BaseClass variable = GetNextSubClass(); //On first iteration GetNextSublass returns an instance of SubClass1 and on second iteration it returns an instance of SubClass2
    variable.SomeMethod();
}

The reason I want to have a generic implementation in the base class is because the implementation for the two sub classes would be exactly the same except for the type

Upvotes: 0

Views: 127

Answers (2)

KiwiPiet
KiwiPiet

Reputation: 1334

Add the generic type to the Base class:

abstract class BaseClass<T>
{
    void SomeMethod<T>()
    {
        ...
    }
}

class SubClass1 : BaseClass<string>
{
    ...
}

class SubClass2 : BaseClass<int>
{
    ...
}

The above code is a bit pointless as we are not making use of the generic types.

abstract class BaseClass<T>
{
    public T SomeMethod<T>(T aParam)
    {
        ...
        return aParam;
    }
}

class SubClass1 : BaseClass<string>
{
    ...
}

class SubClass2 : BaseClass<int>
{
    ...
}

Providing a bit more concrete example of what you want to achieve will be helpful though.

Upvotes: 3

Tanuki
Tanuki

Reputation: 869

It looks like you want to use generic interface:

using System;

class Program
{
    interface IBase<T>
    {
        void SomeMethod();
    }

    class SubClass1 : IBase<string>
    {
        public void SomeMethod()
        {
            Console.WriteLine("I write string!");
        }
    }

    class SubClass2 : IBase<int>
    {
        public void SomeMethod()
        {
            Console.WriteLine("I write int!");
        }
    }

    static void Main(string[] args)
    {
        IBase<string> instance1 = new SubClass1();
        IBase<int> instance2 = new SubClass2();
        instance1.SomeMethod(); //this should call SomeMethod<string>()
        instance2.SomeMethod(); //this should call SomeMethod<int>()

        Console.ReadLine();
    }
}

In fact, you don't even need 2 classes. You could use a single generic class for the same effect:

using System;

class Program
{
    interface IBase
    {
        void SomeMethod();
    }

    class SubClass<T> : IBase
    {
        public void SomeMethod()
        {
            Console.WriteLine("I write {0}", typeof(T));
        }
    }

    static void Main(string[] args)
    {
        IBase instance1 = new SubClass<string>();
        IBase instance2 = new SubClass<int>();
        instance1.SomeMethod(); //this should call SomeMethod<string>()
        instance2.SomeMethod(); //this should call SomeMethod<int>()

        Console.ReadLine();
    }
}

Upvotes: 0

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