Converting ArrayList to Array / Array to ArrayList C#

This article explains the easiest way to convert Array object into ArrayList and the reverse. Author: Aldwin Enriquez

aldwin.net

Posted Date: 06 Dec, 2005

.NET Classes used :

System.Collections.ArrayList

Introduction

Manipulating arrays is one among the most common task in an application development. There were times you need to use array of objects to use the power of object properties and there were times you might like to use an ArrayList for flexibility. Sometimes switching back and forth between these two objects becomes a royal pain in the neck. This article leads you the way on how to do things better

The hard way

Mostly beginners do this conversion manually. In the case of converting from object array into an ArrayList, one might instantiate a new ArrayList then iterates through each object in the array and add it to the ArrayList.

Lets assume we have an object called Person. Typically here is what is commonly done:

Person[] personArray = myPerson.GetPersons();

ArrayList personList = new ArrayList();

foreach(Person objPerson in personArray)

{

personList.Add(objPerson);

}

And creating an object array from an ArrayList might be coded this way

Person[] personArrayFromList = new Person[personList.Count];

int arrayCounter = 0;

foreach(Person objPerson in personList)

{

personArrayFromList.SetValue(objPerson,arrayCounter++);

}

The easy one

But why do it that way while we can just use built-in methods within the .NET classes.

To perform conversions from object array to an ArrayList use the ArrayList.Adapter method. This method takes an IList to be wrapped into an ArrayList. Now the procedure above can be coded like this:

Person[] personArray = myPerson.GetPersons();

ArrayList personList = ArrayList.Adapter(personArray);

To perform conversions from ArrayList to object array use the ArrayList.ToArray method. Now the procedure above can be coded like this:

Person[] personArrayFromList = (Person[])personList.ToArray(typeof(Person));

Don’t forget the casting preceding the arraylist.ToArray method, otherwise you’ll get an error message at compile time saying you can’t convert that arraylist into Person array.

Summary

So next time you convert an object array to arraylist use the static ArrayList.Adapter method and doing the reverse use the ToArray method of the arraylist object.

posted on 2007-09-29 16:58 Robot·H 阅读(218) 评论(0) 编辑收藏所属分类: C#2.0

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