About lists and arrays in UiPath RPA

What is a 'List' variable type?

The List<T>  is a data structure part of the System.Collections.Generic namespace consisting of objects of the same data type. The '<T>' represents the type of elements in the list, for example strings or integers.

Each object has a fixed position in the list, and thus it can be accessed by the specific index. Additionally, it provides methods for searching, sorting, and manipulating lists.

What is an 'IList' variable type?

The IList is actually an Interface. In other words, it is a collection of objects that can be accessed individually by their specific indexes. As in the case of List, the '<T>' represents the type of elements in the list. The IList<T> generic interface is a descendant of the ICollection<T> generic interface and is the base interface of all generic lists.

Both List and IList type of variables can be initialized with 'new list (of...)'. For example, if we have a List of IList of String elements type, looking like 'List<IList<String>>', we can write the following value in the Default value field to initialize it:

new List (of IList(of String))

The same initialization value applies for the 'IList<List<String>>' type of variable.

What is the difference between lists and arrays?

To begin with, both lists and arrays are collection types of variables.

The array variable enables you to store multiple values of the same type. UiPath Studio supports as many types of arrays as it does types of variables. This means that you can create an array of numbers, one of strings, one of Boolean values and so on.
While arrays are fixed-size structures for storing multiple objects, lists allow us to add, insert, and remove items.
If you want to work with a collection that doesn’t have a fixed number of elements, you can use a list instead of an array

Here are some collection-specific activities that we can use in Studio:

Build Collection
Creates a collection of items that have the same type as the first specified element. Learn more about it here(opens in a new tab).

Remove from Collection
Removes the specified item from the specified collection. Learn more about it here(opens in a new tab).

Exists in Collection
Indicates whether a given item is present in a given collection by giving a Boolean output as the result. We can use this activity to check whether a list of clients contains a specific name. Learn more about it here(opens in a new tab).

Append item to Collection
Appends one or more items at the end of the specified collection. Learn more about it here(opens in a new tab).

Merge Collections
Combines the elements of two collections in a new collection or an existing one. Learn more about it here(opens in a new tab).

Filter Collection
Filters a collection based on the specified conditions. Learn more about it here(opens in a new tab).

Collection to Data Table
Converts a specified collection to a DataTable. Learn more about it here(opens in a new tab).

Source: UiPath Academy