Linq Prepend Method

Linq Prepend Method With an Example

In this article, I am going to discuss the LINQ Prepend Method with an example. Please read our previous article before proceeding to this article where we discussed the LINQ Append Method with an example.

Prepend Method:

The Linq Prepend Method is used to add one value to the beginning of a sequence. This Prepend method like Append method does not modify the elements of the sequence. Instead, it creates a copy of the sequence with the new element. The signature of this is given below.

Linq Prepend Method Signature

Type Parameters
  1. TSource: The data type of the elements contained in the sequence.

Parameters:

  1. IEnumerable<TSource> source: A sequence of values.
  2. TSource element: The value to prepend at the beginning of the sequence.

Returns:

  1. IEnumerable<TSource>: A new sequence that begins with the element.

Exceptions: When the source is null, it will throw ArgumentNullException.

Note: This method is support from Framework 4.7.1 or later.

Example:

The following example shows how to prepend a value to the beginning of the sequence using the Prepend method. The following example code is self-explained. So, please go through the comment lines.

using System.Linq;
using System.Collections.Generic;
using System;
namespace LinqDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            // Creating a list of numbers
            List<int> numberSequence = new List<int> { 10, 20, 30, 40 };

            // Trying to prepend 50
            numberSequence.Prepend(50);

            // It will not work because the original sequence has not been changed
            Console.WriteLine(string.Join(", ", numberSequence));

            // It works now because we are using a changed copy of the original list
            Console.WriteLine(string.Join(", ", numberSequence.Prepend(50)));

            // If you prefer, you can create a new list explicitly
            List<int> newnumberSequence = numberSequence.Prepend(50).ToList();

            // And then write to the console output
            Console.WriteLine(string.Join(", ", newnumberSequence));

            Console.ReadKey();
        }
    }
}

Output:

Linq Prepend Method Output

In the next article, I am going to discuss the LINQ ZIP Method with an example. Here, in this article, I try to explain the Prepend Method in Linq with an example.

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