CODEWITHSUNDEEP
c#.net
tsturzl
tsturzl

Reputation: 3137

C# override instance method

So basically I have an object that takes instances and adds them to a list. Each instance uses virtual methods, which I need to override once the instance is created. How would I go about overriding methods of an instance?

Upvotes: 6

Views: 12498

Answers (3)

Peter Rasmussen
Peter Rasmussen

Reputation: 16922

That's not possible at runtime. You cannot change a class' behaviour once it has been instantiated. You could however look into creating a delegate method.

EDIT, just saw the first answer, go with that ;)

Upvotes: 0

Jason Meckley
Jason Meckley

Reputation: 7591

C# is static once the object is created you cannot change the behavior of the object. you can subclass a superclass using inhertance, but this is done at designtime, not runtime.

class foo
{
    public virtual void dosomething()
    {
         console.writeline("this is foo");
    }
}

class bar : foo
{
    public override void dosomething()
    {
         console.writeline("this is bar");
    }
}

var list = new Foo[]{new foo(), new bar()};

There is also the concept of AOP - aspect oriented programming. This is where you can begin to inject behavior at runtime. there are 2 frameworks that I'm aware of that do this

  1. Castle Dynamic Proxy
  2. Spring.Net

Upvotes: 0

Justin Niessner
Justin Niessner

Reputation: 245389

You can't. You can only override a method when defining a class.

The best option is instead to use an appropriate Func delegate as a placeholder and allow the caller to supply the implementation that way:

public class SomeClass
{
    public Func<string> Method { get; set; }

    public void PrintSomething()
    {
        if(Method != null) Console.WriteLine(Method());
    }
}

// Elsewhere in your application

var instance = new SomeClass();
instance.Method = () => "Hello World!";
instance.PrintSomething(); // Prints "Hello World!"

Upvotes: 16

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