[C#] Array Resizing

[Blackout]

How do I resize an array without losing the contents of the array?

  Quote

string[] arr;

...

arr = new string[5];

arr[4] = "Data";

In the above example, whenever I use "arr = new string[5];" it completely wipes the previous array data and the only data that exists is arr[4]. How do I resize an array without losing the data?

Thanks in advance.

[karma_police]

As far as I know you cant, why dont you use an ArrayList?

[lexecutil]

You will have to copy the contents of the old array into the new one. :) Or of course there are dynamic object collection objects like ArrayList which will do that all for you, though with a slight hit on performance.

Dan

[turbowrx]

You could use an arraylist, which allows you to continue to change the size of the array. If you use normal arrays, you will have to create a new one and then copy the old array into the new array.

[karma_police]

haha 3 answers almost at the same time.

[+chorpeac MVC]

You have discovered the reason to have the Arraylist!! It's a dynamically growing data structure. In this case, I think the arraylist would be your best bet, and you won't see much performance degradation.

[Blackout]

So how would I go about converting an Arraylist to a string[]?

[Winston]

Hmmm, like many said i think there's no ultimate solution besides moving to ArrayList, if you're pretty sure your collection won't grow to extreme amounts then you can probably just make a method that will merge existing data from an array into a new sized array, very easily done.

ArrayList do have a performance hit as mentioned, furthermore, you have to do type-casting and that's another issue, but i think you shouldn't need to worry too much about these factors, as the framework handles it pretty well.

[+virtorio MVC]

  Blackout said:

So how would I go about converting an Arraylist to a string[]?

585068903[/snapback]

  ArrayList al = new ArrayList;

  //
  // ... Fill array list with string here
  //     such as al.Add("hello //

  string[] s = new string[al.Count];
  for (int i=0; i < al.Count; i++)
      s[i] = (string)al[i];

[Winston]

  Blackout said:

So how would I go about converting an Arraylist to a string[]?

585068903[/snapback]

You mean the other way arround?

ArrayList stringCollection = new ArrayList();

stringCollection.add(yourString);

The good thing with using ArrayList is you don't have to specify the size, the size is dynamically changed accordingly during run-time as the list becomes filled with Objects.

[Blackout]

Nevermind, I solved it all. Thanks though!

[azcodemonkey]

You could also use the CopyTo method to copy the contents in one shot.

ArrayList al = new ArrayList();

// ... add strings

string[] s = new string[al.Count];
al.CopyTo(s, 0);

Note that if your ArrayList contains things other than strings, you'll get an exception. That's really the only downside to using the ArrayList. It's not typesafe. You could create your own strongly typed collection by making a class that inherits from CollectionBase. OR, you could use the StringCollection in System.Collections.Specialized(saved the best for last).

[Sn1p3t]

  weenur said:

You could also use the CopyTo method to copy the contents in one shot.

ArrayList al = new ArrayList();

// ... add strings

string[] s = new string[al.Count];
al.CopyTo(s, 0);

Note that if your ArrayList contains things other than strings, you'll get an exception. That's really the only downside to using the ArrayList. It's not typesafe. You could create your own strongly typed collection by making a class that inherits from CollectionBase. OR, you could use the StringCollection in System.Collections.Specialized(saved the best for last).

585070088[/snapback]

And that's why I can't wait for generics (.NET 2.0).

ArrayList<string> s = new ArrayList<string>;

:D

[azcodemonkey]

  Sn1p3t said:

And that's why I can't wait for generics (.NET 2.0).

ArrayList<string> s = new ArrayList<string>;

:D

585070128[/snapback]

Can I get an amen!? :p

I've been playing with generics a bit. They're cool, but still not as cool as C++ templates.

[MrRogers]

Hey, has anyone mentioned using an ArrayList? :rofl:

[azcodemonkey]

  MrRogers said:

Hey, has anyone mentioned using an ArrayList?  :rofl:

585071782[/snapback]

That's a great idea! :laugh: