Sure, I can help you with that.

To use a lambda expression in Enumerable.Distinct(), you need to pass the lambda expression as the predicate parameter to the Distinct() method. The predicate parameter is a function that takes two elements of the sequence as its parameters and returns a boolean value. The Distinct() method will return a sequence that contains only the elements of the original sequence for which the predicate returns true.

Here is an example of how to use a lambda expression in Enumerable.Distinct():

C#

using System;
using System.Collections.Generic;

namespace DistinctLambdaExpression
{
    public class Program
    {
        public static void Main(string[] args)
        {
            // Create a list of numbers.
            List<int> numbers = new List<int>();
            numbers.Add(1);
            numbers.Add(2);
            numbers.Add(3);
            numbers.Add(1);
            numbers.Add(2);

            // Use a lambda expression to remove duplicate numbers.
            List<int> distinctNumbers = numbers.Distinct((x, y) => x != y);

            // Print the distinct numbers.
            foreach (int number in distinctNumbers)
            {
                Console.WriteLine(number);
            }
        }
    }
}

In this example, the lambda expression takes two integers as its parameters and returns a boolean value. The lambda expression returns true if the two integers are not equal, and false if the two integers are equal. The Distinct() method will return a sequence that contains only the elements of the original sequence for which the predicate returns true.