System.ArrayList Class using VB.NET

The ArrayList class implements a collection of objects using an array whose size is dynamically increased as required. The ArrayList class is very useful if you are working with arrays and need to add, remove, index, or search for data in a collection.

Although ArrayList is very versatile and grows dynamically when you add values, it is slower than the Array class, which allows you to access its members with subscripts but does not let the array grow during runtime. When choosing between Array and ArrayList, decide which feature is important to your application. To get a better idea of how an Array compares to an ArrayList, think of an ArrayList as nothing more than a linked-list implementation of an Array. Adding data to an ArrayList is pretty easy; just call the class's Add member, as shown in below example.

Example of Adding an element to an ArrayList

    Imports System.Collections.Generic
    Imports System.Linq
    Imports System.Text
    Imports System.Collections
    Namespace systemArrayListClass
        Class Program
            Shared Sub Main(ByVal args As String())
                Dim dataArray As New ArrayList()
                For i As Integer = 0 To 19
                    dataArray.Add(i)
                Next
                ' or you can add any object type like below.
                dataArray.Add("Object type")
            End Sub
        End Class
    End Namespace

You can also insert an element into the ArrayList at a specified index. Note that if you specify the index item as the last item + 1, the Insert method works the same way as the Add method:

           myList.Insert(1, "real first")

The Remove and RemoveAt members delete data from an ArrayList. The RemoveAt method removes the element at the specified index of the ArrayList, while the Remove method removes the first occurrence of a specific object from the ArrayList:

           myList.Remove("3") // Remove the element containing "3". 

The BinarySearch member of ArrayList is very useful and fast for searching for elements. This member returns the zero-based index of a specific element in the sorted ArrayList or a portion of it using a binary search algorithm:

            Dim myIndex As Integer = myList.BinarySearch(3)

With the ToArray function, you can copy the elements of the ArrayList to a new array of the specified type:

            Dim myIntArr As Integer() = myList.ToArray(Int32)

You can always set the capacity to the actual number of elements in the ArrayList with the TrimToSize function:

            myList.TrimToSize()

Conclusion

Hope this article would have helped you in understanding the System.ArrayList Class using VB.NET.