[1.0/1.1] Copying an ArrayList to another

[drattansingh]

Hi. I'm passing an arraylist to a method in which I want to copy it. I did it as:

ArrayList al....

add values to al....

call method: method(al)

...


another class:
ArrayList te;

.....

public void method(ArrayList al)
{ te = al;
}


Now it is assigning, but if I'm back in the original class and I change ArrayList al, the value of te is also changing. Does anyone knows how to fix this problem? I just want to copy the value of al to te in the method, not the actual pointer to the ArrayList.

[drattansingh]

This is working:

for(int x=0 ; x<al.Count ; x++)
{
this.te.Add(al[x].ToString());

}


But is there a shorter way of doing this?

[ComputerJy]

use:

mySourceArray.CopyTo(myTargetArray, Index);

[drattansingh]

use:

mySourceArray.CopyTo(myTargetArray, Index);

Its:

Array.Copy(source, 0, Dest, 0, source.count);


But you have to convert the arrayLists as Arrays. I don't want to convert the ArrayLists to arrays, I want when it is finished copying, the dest and source are still both arraylists.

[ComputerJy]

No, I'm talking about srcArray.CopyTo()
it's not a static method, so you can call it from an instance of the ArrayList

[drattansingh]

I'm getting this error:

Argument '2': cannot convert from 'System.Collections.ArrayList' to 'System.Array'


from this code:

Main.CopyTo(0, CopyValue, 0, Main.Count);


where main is the source arraylist and CopyValue is the destination arraylist.
I also tried

Main.CopyTo(CopyValue, 0);

But I was getting the following error

The best overloaded method match for 'System.Collections.ArrayList.CopyTo(System.Array, int)' has some invalid arguments

[ComputerJy]

Sorry, it seems that CopyTo only copies into an array.
use:

ArrayList b=arrayListA.Clone();

This is supposed to work (hopefully)

[ComputerJy]

or you can do this:

arrayListB = arrayListA.GetRange(0, arrayListA.Count);

[drattansingh]

I got figured it out:

ArrayList al....

add values to al....

call method: method(al)

...


another class:
ArrayList te;

.....

public void method(ArrayList al)
{ // te = al; -> this is wrong since it would copy the actual pointer to al, so
// if I change te, al will also be changed.

te = new ArrayList(al); // This is copy by value only not pointers!
}


Thanks computer jr

[jmcilhinney]

You should use the Clone method as cj suggested in post #7. Clone is the standard way to create a shallow copy of an object, assuming that the type implements IClonable, which Clone is a member of.