Dynamic Instantiation

[Fariba]

Sorry if this sounds like a newbie question.

I have two classes in my app, A & B. each class has a public method called
"EchoTime() ". In my UI ,user chooses wether to call EchoTime() from A or B
and then I have to dynamically instantiate the appropriate class and call tis
method.

1) How can I do that?

2) Is it the concept of late binding?

Thanks

[gmiley]

Re: Dynamic Instantiation

One way to do this would be to have a base class or interface that has
EchoTime() in it:

public class TimeEcho
{
public void EchoTime()
{
// Do something
}
}

Then you could have classes A & B defined inheriting from TimeEcho:

public class A : EchoTime
{

}

public class B : EchoTime
{

}

Then depending on what the user selects:

public void DoUsersChoice(s tring className)
{
EchoTime userSelectedCla ss =
(EchoTime)Type. GetType(classNa me).GetConstruc tor(new Type[] {
}).Invoke(new object[] { });
userSelectedCla ss.EchoTime();
}

Fariba wrote:[color=blue]
> Sorry if this sounds like a newbie question.
>
> I have two classes in my app, A & B. each class has a public method called
> "EchoTime() ". In my UI ,user chooses wether to call EchoTime() from A or B
> and then I have to dynamically instantiate the appropriate class and call tis
> method.
>
> 1) How can I do that?
>
> 2) Is it the concept of late binding?
>
> Thanks[/color]

[gmiley]

Re: Dynamic Instantiation

Sorry those classes should have been defined as:

public class A : TimeEcho
{

}

public class B : TimeEcho
{

}


gmiley wrote:[color=blue]
> One way to do this would be to have a base class or interface that has
> EchoTime() in it:
>
> public class TimeEcho
> {
> public void EchoTime()
> {
> // Do something
> }
> }
>
> Then you could have classes A & B defined inheriting from TimeEcho:
>
> public class A : EchoTime
> {
>
> }
>
> public class B : EchoTime
> {
>
> }
>
> Then depending on what the user selects:
>
> public void DoUsersChoice(s tring className)
> {
> EchoTime userSelectedCla ss =
> (EchoTime)Type. GetType(classNa me).GetConstruc tor(new Type[] {
> }).Invoke(new object[] { });
> userSelectedCla ss.EchoTime();
> }
>
> Fariba wrote:[color=green]
> > Sorry if this sounds like a newbie question.
> >
> > I have two classes in my app, A & B. each class has a public method called
> > "EchoTime() ". In my UI ,user chooses wether to call EchoTime() from A or B
> > and then I have to dynamically instantiate the appropriate class and call tis
> > method.
> >
> > 1) How can I do that?
> >
> > 2) Is it the concept of late binding?
> >
> > Thanks[/color][/color]

[Fariba]

Re: Dynamic Instantiation

Thanks for your reply,

Which concept of oo this approach is refering to?

Thanks

"gmiley" wrote:
[color=blue]
> Sorry those classes should have been defined as:
>
> public class A : TimeEcho
> {
>
> }
>
> public class B : TimeEcho
> {
>
> }
>
>
> gmiley wrote:[color=green]
> > One way to do this would be to have a base class or interface that has
> > EchoTime() in it:
> >
> > public class TimeEcho
> > {
> > public void EchoTime()
> > {
> > // Do something
> > }
> > }
> >
> > Then you could have classes A & B defined inheriting from TimeEcho:
> >
> > public class A : EchoTime
> > {
> >
> > }
> >
> > public class B : EchoTime
> > {
> >
> > }
> >
> > Then depending on what the user selects:
> >
> > public void DoUsersChoice(s tring className)
> > {
> > EchoTime userSelectedCla ss =
> > (EchoTime)Type. GetType(classNa me).GetConstruc tor(new Type[] {
> > }).Invoke(new object[] { });
> > userSelectedCla ss.EchoTime();
> > }
> >
> > Fariba wrote:[color=darkred]
> > > Sorry if this sounds like a newbie question.
> > >
> > > I have two classes in my app, A & B. each class has a public method called
> > > "EchoTime() ". In my UI ,user chooses wether to call EchoTime() from A or B
> > > and then I have to dynamically instantiate the appropriate class and call tis
> > > method.
> > >
> > > 1) How can I do that?
> > >
> > > 2) Is it the concept of late binding?
> > >
> > > Thanks[/color][/color]
>
>[/color]

[Fariba]

Re: Dynamic Instantiation

I created an Interface called IEchoTime and made both classes implement the
interface. When I use your code I get "object reference not set to an
instance of an object"

Your help is apppreciated.

Thanks

"gmiley" wrote:
[color=blue]
> Sorry those classes should have been defined as:
>
> public class A : TimeEcho
> {
>
> }
>
> public class B : TimeEcho
> {
>
> }
>
>
> gmiley wrote:[color=green]
> > One way to do this would be to have a base class or interface that has
> > EchoTime() in it:
> >
> > public class TimeEcho
> > {
> > public void EchoTime()
> > {
> > // Do something
> > }
> > }
> >
> > Then you could have classes A & B defined inheriting from TimeEcho:
> >
> > public class A : EchoTime
> > {
> >
> > }
> >
> > public class B : EchoTime
> > {
> >
> > }
> >
> > Then depending on what the user selects:
> >
> > public void DoUsersChoice(s tring className)
> > {
> > EchoTime userSelectedCla ss =
> > (EchoTime)Type. GetType(classNa me).GetConstruc tor(new Type[] {
> > }).Invoke(new object[] { });
> > userSelectedCla ss.EchoTime();
> > }
> >
> > Fariba wrote:[color=darkred]
> > > Sorry if this sounds like a newbie question.
> > >
> > > I have two classes in my app, A & B. each class has a public method called
> > > "EchoTime() ". In my UI ,user chooses wether to call EchoTime() from A or B
> > > and then I have to dynamically instantiate the appropriate class and call tis
> > > method.
> > >
> > > 1) How can I do that?
> > >
> > > 2) Is it the concept of late binding?
> > >
> > > Thanks[/color][/color]
>
>[/color]

[Guest]

Re: Dynamic Instantiation

Why use reflection for such a small thing?
Cant the code be written like this?

if (classname == "A")
{
A obj = new A();
obj.EchoTime();
}
else
{
B obj = new B();
obj.EchoTime();
}

HTH
Kalpesh

[Fariba]

Re: Dynamic Instantiation

It is not small thing.I made it small so people can answer me.If I follow
what you suggest (Like what to came to my mind at the beggining) , I have to
duplicate lines of code for each condition ,don't you think it is not as
pretty as you do it dynamically?

Thanks

"<Kalpesh/>" wrote:
[color=blue]
> Why use reflection for such a small thing?
> Cant the code be written like this?
>
> if (classname == "A")
> {
> A obj = new A();
> obj.EchoTime();
> }
> else
> {
> B obj = new B();
> obj.EchoTime();
> }
>
> HTH
> Kalpesh
>[/color]