> For the complete documentation index, see [llms.txt](https://docs.shouldly.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.shouldly.org/documentation/enumerable/unique.md).

# Unique

```cs
var lisa = new Person { Name = "Lisa" };
var bart = new Person { Name = "Bart" };
var maggie = new Person { Name = "Maggie" };
var simpsonsKids = new List<Person> { bart, lisa, maggie, maggie };
simpsonsKids.ShouldBeUnique();
```

[snippet source](https://github.com/shouldly/shouldly/blob/master/src/DocumentationExamples/CodeExamples/EnumerableShouldBeUniqueExamples.ShouldBeUnique.codeSample.approved.cs#L1-L5) | [anchor](#snippet-EnumerableShouldBeUniqueExamples.ShouldBeUnique.codeSample.approved.cs)

**Exception**

```
simpsonsKids
    should be unique but
[Maggie]
    was duplicated
```