First

If you ever need to return the first element in an array or list, First is a useful method to use as it does just that.

Basic example

For this list, using First will return the first element in the array which will be 2.

Live example: https://dotnetfiddle.net/SbPB7D

var numbers = new[] { 2, 4, 6, 8, 10 };

int first = numbers.First();

//output: 2  

First with Predicate

Just like the First method where it returns the first element of an array or list, you can use the First operator to return the first element based on a boolean condition.

In this example, we have a list of people and we just want to pull out Carrie from the list which has an id of 3.

We can perform this with either a Where clause with a combination of a .First or alternatively we can use the .First with a predicate.

Where with First

Here's an example with the combination of using .Where and .First.

Live example: https://dotnetfiddle.net/dOQW5C

var people = new[]
    {
        new
            {
                Id =1, Name = "Vernon", Gender = "Male", CountryCode = "GB",
            },
        new
            {
                Id = 2, Name = "Carrie", Gender = "Female", CountryCode = "CA"
            },
        new
            {
                Id = 3, Name = "Joanna", Gender = "Female", CountryCode = "US"
            },
    };

var carrie = people.Where(p => p.Id == 3).First();

//output: carrie

First with predicate example

Here's an example with a predicate.

Live example: https://dotnetfiddle.net/5Xvty9

var people = new[]
    {
        new
            {
                Id = 1, Name = "Vernon", Gender = "Male", CountryCode = "GB",
            },
        new
            {
                Id = 2, Name = "Carrie", Gender = "Female", CountryCode = "CA"
            },
        new
            {
                Id = 3, Name = "Joanna", Gender = "Female", CountryCode = "US"
            },
    };

var carrie = people.First(p => p.Id == 3);

//output: carrie