更新：从用户控件上的自定义控件覆盖方法

Question

good morning.

this is something that I'd like to achieve.

for CustomControlA , I have

public void OverrideableMethod()
{
// some codes here
}

and I have UserControlB . I would like to "override" the method from CustomControlA on UserControlB . is this possible? if it is, how to?

the best thing I can come up is to create a method of the same name on UserControlB and invoke CustomControlA.OverrideableMethod() from there.

---

Update: Thanks for the answers, I appreciate them.

the code is something like this:

public class CustomControlA : CustomControl
{
    public virtual void OverrideableMethod()
    {
        // do something
    }
}

public class UserContorlB : System.Web.UI.UserControl
{
    protected CustomControlA someVariableForCustomControlA;

    // here lies the problem, on how to override CustomControlA.OverrideableMethod() here
    // without inheriting CustomControlA itself
}

here lies to problem. as much as possible, I'd want to keep away from inheriting CustomControlA, for reasons allowing UserControlB to inherit one more base class. is this possible to override CustomControlA.OverrideableMethod() given the scenario above?

Answer 1

You need to use virtual and override keywords to override the methods in the child class if at all UserControlB is a child class of CustomControlA. If not then its not method overriding.

public class CustomControlA
{
     public virtual void OverrideableMethod()
     {
      // some codes here
      }
}

public class UserControlB: CustomControlA
{
     public override void OverrideableMethod()
     {
         // some codes here
     }

}

UPDATE (based on the updated part of your question): No its not possible to do the overriding(actually you are not even trying to do overriding) but you can do something like below. You should always call UserContorlB.OverrideableMethod() but make sure you have some condition based on which the proper method will be called.

public class CustomControlA
{
    public void OverrideableMethod()
    {
        // do something
    }
}

public class UserContorlB : System.Web.UI.UserControl
{
    protected CustomControlA someVariableForCustomControlA;

    public void OverrideableMethod()
    {
        if(some condition is true)
        {
             someVariableForCustomControlA.OverrideableMethod();
        }
        else 
        {
             // do some logic here
        }   
    }
}

Answer 2

You should post your code for the controls to make this clear.

It is possible under the following conditions, and btw you wouldn't be invoking CustomControlA.OverrideableMethod() from UserControlB. If UserControlB inherited CustomControlA then the method exists in UserControlB:

public class CustomControlA : UserControl
{

    public virtual void OverrideableMethod() {  /* code the default implementation */ }
}

Your UserControlB would extend/inherit CustomControlA

public class UserControlB : CustomControlA
{

    public override void OverrideableMethod() {  /* implement whatever you want */ }
}

If CustomControlA's method had code you wanted to execute as well as NEW code in UserControlB you would do this:

public class UserControlB : CustomControlA
{

    public override void OverrideableMethod() 
    {
         base.OverrideableMethod();
         /*
            additional code here
         */  
    }
}

The best practice for inherited methods when building base classes that will fire descendant code is as follows:

public class CustomControlA : UserControl
{

    public void OverrideableMethod() 
    {
       //You can code here for things before the overrideable method
       OnOverrideableMethod();
       //You can code here for things after the overrideable method
    }

    protected virtual void OnOverrideableMethod() { }
}


public class UserControlB : CustomControlA
{

    protected override void OnOverrideableMethod() 
    {
       /*  implement here */
    }
}

This prevents any direct calls to the "OnXXXX" methods and forces calls to the public/well defined methods. It provides you the ability to add code before and/or after the "OnXXX" method.