Easy way to cast an object array into another type in C#

Question

I want to be able to be able to quickly cast an array of objects to a different type, such as String, but the following code doesn't work:

String[] a = new String[2];
a[0] = "Hello";
a[1] = "World";
ArrayList b = new ArrayList(a);
String[] c = (String[]) b.ToArray();

And I don't want to have to do this:

String[] a = new String[2];
a[0] = "Hello";
a[1] = "World";
ArrayList b = new ArrayList(a);
Object[] temp = b.ToArray();
String[] c = new String[temp.Length];
for(int i=0;i<temp.Length;i++)
{
    c[i] = (String) temp[i];
}

Is there an easy way to do this without using a temporary variable? Edit: This is in ASP.NET, by the way.

Man, how long will it take for people to stop using ArrayList? — ChaosPandion
– ChaosPandion, Commented Jun 12, 2010 at 22:30
Use generic collections in place of ArrayList. Generics are completely type-safe in a way that ArrayList could never possibly be. — Cylon Cat
– Cylon Cat, Commented Jun 12, 2010 at 22:50
I hope my comment wasn't taken the wrong way. It is just one of my pet peeves. — ChaosPandion
– ChaosPandion, Commented Jun 12, 2010 at 23:01
It's actually a very good questions and generics sometimes don't help at all. Let's say you have a generic piece of code running on an List<object> and a more specific one requiring a List<string>. Now another piece of code uses both methods. How would you do that? Even if you use generics all over the shop. — Alex
– Alex, Commented Jun 13, 2010 at 8:15

ChaosPandion · Accepted Answer · 2010-06-12 22:40:11Z

6

The best solution would be to use a List<string>.

answered Jun 12, 2010 at 22:40

ChaosPandion

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1 Comment

spender Over a year ago

...and welcome to a new world ;) It's seriously worth getting your head around generics.

tzaman · Accepted Answer · 2010-06-12 22:45:33Z

4

Use LINQ:

String[] c = b.Cast<String>().ToArray();

May I ask why you're using ArrayList in the first place, instead of a generic collection type?

edited Jun 12, 2010 at 22:45

answered Jun 12, 2010 at 22:33

tzaman

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Comments

Diego Pereyra · Accepted Answer · 2010-06-12 22:37:08Z

1

You can do something like

myArray.Select(mySomething => new SomethingElse(mySomething)).ToArray()

to cast it to anything you like :)

answered Jun 12, 2010 at 22:37

Diego Pereyra

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Marius Schulz · Accepted Answer · 2010-06-14 18:57:02Z

0

+1 for the generic Collections such as List<T>, -1 for ArrayList which is better be put on mothballs.

answered Jun 14, 2010 at 18:57

Marius Schulz

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