Checking if a collection is empty in C#

In C#, there are several ways to check if a collection is empty. Depending on the collection type, you can use the Length, Count, or IsEmpty property, or the Enumerable.Any() extension method.

// array: Length
int[] array = ...;
var isEmpty = array.Length == 0;

// List: Count
List<int> list = ...;
var isEmpty = list.Count == 0;

// ImmutableArray<T: IsEmpty
ImmutableArray<int> immutableArray = ...;
var isEmpty = immutableArray.IsEmpty;

// Span: IsEmpty
Span<int> span = ...;
var isEmpty = span.IsEmpty;

// Extension method
List<int> list = ...;
var isEmpty = !list.Any();
var isEmpty = list.All(item => false);

With C# 11, you can use pattern matching to let the compiler choose the best method to check if the collection is empty. You no longer need to remember the correct property name.

var collection = ...;
var isEmpty = collection is []; // Works for any collection type

Note that this approach is not exactly equivalent to checking the Length property. If the collection is null, checking the property throws a NullReferenceException, while pattern matching returns false.

int[] array = null;
var isEmpty = array.Length == 0; // NullReferenceException
var isEmpty = array is [];       // false

If you want to check if a collection is null or empty, you can use the following code:

var isNullOrEmpty = array is null or [];

Note that you can use the same logic to check if a string is empty:

// Both are equivalent, but string.IsNullOrEmpty(value) may be more common 😉
string str = "";
isEmpty = str is "";
isEmpty = str is [];

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