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What is the difference between "ToList()" and "ToArray()" when materializing LINQ queries?

Steilla Mitchel17712-Sep-2023

What is the difference between "ToList()" and "ToArray()" when materializing LINQ queries?

c# c#  linq 
Updated on 25-Sep-2023
Steilla Mitchel

Steilla Mitchel

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Aryan Kumar

Aryan Kumar

25-Sep-2023

ToList() and ToArray() are methods in LINQ that are used to materialize (convert) the results of a LINQ query into different collection types: List<T> and T[] (array), respectively. While they serve a similar purpose, there are some key differences between the two:

Return Type:

  • ToList(): It returns a List<T> that contains the results of the query.
  • ToArray(): It returns an array (T[]) that contains the results of the query.

Type Flexibility:

  • ToList() returns a List<T>, which is a dynamic, resizable collection. You can add or remove items from it, and it's well-suited for scenarios where you need to work with a collection that can grow or shrink.
  • ToArray() returns a fixed-size array (T[]). Once the array is created, you cannot change its size. It's suitable when you need an immutable, fixed-size collection.

Performance:

  • ToList() can be more efficient than ToArray() in cases where the final size of the collection is not known in advance because it doesn't require resizing operations like an array.
  • ToArray() can be more efficient in scenarios where you know the exact size of the collection in advance because it avoids the overhead of resizing.

API and Methods:

  • List<T> provides a richer set of methods and properties compared to arrays. For example, you can use Add(), Remove(), Find(), and more on a List<T>.
  • Arrays (T[]) have a fixed size, and their methods are limited to basic operations like indexing and enumeration.

Memory Consumption:

  • ToList() may consume slightly more memory than ToArray() because it has the flexibility to grow dynamically.
  • ToArray() usually consumes less memory because it preallocates the exact amount of memory required for the elements.

Use Cases:

  • Use ToList() when you need a dynamic, resizable collection and plan to modify or extend the collection.
  • Use ToArray() when you need an immutable, fixed-size collection, or when you know the final size of the collection in advance.

Here's an example of using both methods:

var numbers = Enumerable.Range(1, 5);
// Using ToList()
var list = numbers.ToList(); // Returns List<int>
// Using ToArray()
var array = numbers.ToArray(); // Returns int[]

In summary, the choice between ToList() and ToArray() depends on your specific requirements and how you intend to use the result of the LINQ query. If you need a dynamic, resizable collection, use ToList(). If you need an immutable, fixed-size collection or want to minimize memory usage, use ToArray().

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