dotnet/Documentation/compatibility/enumerable_empty-always-returns-cached-instance.md

Enumerable.Empty<TResult> always returns cached instance

Scope

Edge

Version Introduced

4.5

Source Analyzer Status

Available

Change Description

Beginning in .NET 4.5, xref:System.Linq.Enumerable.Empty``1 always returns a cached internal instance xref:System.Collections.Generic.IEnumerable`1.

Previously, xref:System.Linq.Enumerable.Empty``1 would cache an empty xref:System.Collections.Generic.IEnumerable`1 at the time the API was called, meaning that in some conditions in which xref:System.Linq.Enumerable.Empty``1 was called rapidly and concurrently, different instances of the type could be returned for different calls to the API.

• Quirked
• Build-time break

Recommended Action

Because the previous behavior was non-deterministic, code is unlikely to depend on it. However, in the unlikely case that empty enumerables are being compared and expected to sometimes be unequal, explicit empty arrays should be created (new T[0]) instead of using xref:System.Linq.Enumerable.Empty``1.

Affected APIs

• M:System.Linq.Enumerable.Empty``1

Category

LINQ