> For the complete documentation index, see [llms.txt](https://raviram.gitbook.io/c-programing/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://raviram.gitbook.io/c-programing/linq/methods-returning-single-item.md).

# Methods returning single item

## Methods - Extract a single element

### First() method

Intuitively enough, this extracts the first element in the sequence

```csharp
var doubles = new List<double> { 2.0, 2.1, 2.2, 2.3 };
double whatsThis = doubles.First();

Console.WriteLine(whatsThis);
Console.ReadKey();
```

Conditionally extract the first element

```csharp
List<double> doubles = new List<double> { 2.0, 2.1, 2.2, 2.3 };
double whatsThis = doubles.First(val => val > 2.1);

Console.WriteLine(whatsThis);
Console.ReadKey();
```

> What happens if it was `val > 2.3` ?

### Single() method

Conditionally extract single element

```csharp
List<double> doubles = new List<double> { 2.0, 2.1, 2.2, 2.3 };
double whatsThis = doubles.Single(val => val > 2.2);
```

> What happens if it was `val > 2.1` ?

### FirstOrDefault() method

What do you think this call to `FirstOrDefault`() would return?

```csharp
var doubles = new List<double> { 2.0, 2.1, 2.2, 2.3 };
double whatsThis = doubles.FirstOrDefault(val => val > 2.3);

Console.WriteLine(whatsThis);
Console.ReadKey();
```

### SingleOrDefault() method

`SingleOrDefault()` is a bit different from the others. If there is no element in the list that meets the criteria, then a default value is returned. If more than one value meets the criteria, then `SingleOrDefault()` still throws an exception, just like the `Single()` method.

With this in mind, what do you think this would do?

```csharp
List<double> doubles = new List<double> { 2.0, 2.1, 2.2, 2.3 };
double whatsThis = doubles.SingleOrDefault(val => val > 2.1 && val <= 2.3);

Console.WriteLine(whatsThis);
Console.ReadKey();
```

> Can you try these for your own collection of other data types like string?


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