System.Linq.Enumerable

Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)

Returns distinct elements in the first sequence which are not in the second sequence.

Parameters Description
first<TSource>
IEnumerable<TSource>		 The first IEnumerable<TSource> to project.
second<TSource>
IEnumerable<TSource>		 IEnumerable<TSource> to exclude elements from.
Returns An IEnumerable<TSource> that contains elements from the first sequence that do not appear in the second sequence.
Remarks

The Except method returns elements that are in the first sequence but not in the second. The comparison of elements is done using the default equality comparer for the type of the elements.

For a query to return an error when the sequence is empty, use the ElementAt or First methods.

Example

The following code example demonstrates how to use the Except method to find the difference between two sequences.

using System;
using System.Collections.Generic;
using System.Linq;

public class Example
{
    public static void Main()
    {
        List<int> numbersA = { 0, 1, 2, 3, 4, 5 };
        List<int> numbersB = { 2, 3, 4, 5, 6, 7 };

        // Get the numbers that are in numbersA but not in numbersB.
        IEnumerable<int> differenceQuery = numbersA.Except(numbersB);

        // Use a foreach loop to process the elements in the resulting collection.
        foreach (int number in differenceQuery)
        {
            Console.WriteLine(number); // Output: 0, 1
        }
    }
}

Overloads

The Except method has several overloads to accommodate different comparison needs: