The ```LinkedList<T>``` generic class in the ```System.Collections.Generic``` namespace provides the **```Contains()``` method**, which can be used to determine if a specified value exists in a linked list in C#.

# Syntax
```
public bool Contains (T value);
```
- It takes the `T` value as input, to be searched in the linked list.

- It returns `true` if the value is present in the linked list and `false` otherwise.

# Things to note
- This method is an _O(n)_ operation, as it performs a linear search in the linked list and may have to traverse all the elements in the worst case.

- The input value passed can be `null` for reference types.

## Code example
In the code below, we created a linked list of strings and added the names of few months to it. The linked list contains four strings: `January`, `February`, `March`, and `April`.

We also created a helper method, ```Print()```, to display the linked list nodes.

Now, we call the ```Contains()``` method by passing the `March` string to find it in the list, and it performs a linear search in the list and returns ```true```. This is shown in the output as well.

Next, we call the ```Contains()``` method by passing the input string as `December` to find in the list, and it returns ```false```, as `December` does not exist in the linked list.

>Please note that the ```LinkedList<T>``` class is maintained internally as a doubly-linked list and ```Contains()``` is an _O(n)_ operation.

The program prints the below output and exits.
```
LinkedList Elements
January, February, March, April, 

Does node with value March exists in linked list ? True
Does node with value December exists in linked list ? False
```

using System;
using System.Collections.Generic;

class LinkedListContains
{
    static void Main()
    {
        LinkedList<string> monthList = new LinkedList<string>();
        monthList.AddLast("January");
        monthList.AddLast("February");
        monthList.AddLast("March");
        monthList.AddLast("April");
        Console.WriteLine("LinkedList Elements");
        Print(monthList);
        
        string searchMonth1 = "March", searchMonth2="December";
        bool result = monthList.Contains(searchMonth1);
        Console.WriteLine($"Does node with value {searchMonth1} exist in linked list? {result}");
        result = monthList.Contains(searchMonth2);
        Console.WriteLine($"Does node with value {searchMonth2} exist in linked list? {result}");

    }

    private static void Print(LinkedList<string> list)
    { 
        foreach (var node in list)
        {
            Console.Write(node + ", ");
        }
        Console.WriteLine("\n");        
    }
}

How to determine if a value exists in a linked list in C#

Use the LinkedList<T>.Contains() method in C# to check if a value exists, returning true or false.