Jon Skeet和miguelmpn的回答都很好。这取决于列表元素的顺序是否重要:

// take order into account
bool areEqual1 = Enumerable.SequenceEqual(list1, list2);

// ignore order
bool areEqual2 = !list1.Except(list2).Any() && !list2.Except(list1).Any();

如果只需要组合结果，这也可以工作:

var set1 = new HashSet<T>(list1);
var set2 = new HashSet<T>(list2);
var areEqual = set1.SetEquals(set2);

其中T是列表元素的类型。

第一种方法:

if (list1 != null && list2 != null && list1.Select(x => list2.SingleOrDefault(y => y.propertyToCompare == x.propertyToCompare && y.anotherPropertyToCompare == x.anotherPropertyToCompare) != null).All(x => true))
   return true;

第二种方法，如果你对重复值没有问题:

if (list1 != null && list2 != null && list1.Select(x => list2.Any(y => y.propertyToCompare == x.propertyToCompare && y.anotherPropertyToCompare == x.anotherPropertyToCompare)).All(x => true))
   return true;

我比较了3种不同的方法来比较不同的数据集。下面的测试创建了一个包含从0到length - 1的所有数字的字符串集合，然后是另一个具有相同范围但包含偶数的集合。然后我从第一个集合中挑出奇数。

使用Linq除外

public void TestExcept()
{
    WriteLine($"Except {DateTime.Now}");
    int length = 20000000;
    var dateTime = DateTime.Now;
    var array = new string[length];
    for (int i = 0; i < length; i++)
    {
        array[i] = i.ToString();
    }
    Write("Populate set processing time: ");
    WriteLine(DateTime.Now - dateTime);
    var newArray = new string[length/2];
    int j = 0;
    for (int i = 0; i < length; i+=2)
    {
        newArray[j++] = i.ToString();
    }
    dateTime = DateTime.Now;
    Write("Count of items: ");
    WriteLine(array.Except(newArray).Count());
    Write("Count processing time: ");
    WriteLine(DateTime.Now - dateTime);
}

输出

Except 2021-08-14 11:43:03 AM
Populate set processing time: 00:00:03.7230479
2021-08-14 11:43:09 AM
Count of items: 10000000
Count processing time: 00:00:02.9720879

使用HashSet。添加

public void TestHashSet()
{
    WriteLine($"HashSet {DateTime.Now}");
    int length = 20000000;
    var dateTime = DateTime.Now;
    var hashSet = new HashSet<string>();
    for (int i = 0; i < length; i++)
    {
        hashSet.Add(i.ToString());
    }
    Write("Populate set processing time: ");
    WriteLine(DateTime.Now - dateTime);
    var newHashSet = new HashSet<string>();
    for (int i = 0; i < length; i+=2)
    {
        newHashSet.Add(i.ToString());
    }
    dateTime = DateTime.Now;
    Write("Count of items: ");
    // HashSet Add returns true if item is added successfully (not previously existing)
    WriteLine(hashSet.Where(s => newHashSet.Add(s)).Count());
    Write("Count processing time: ");
    WriteLine(DateTime.Now - dateTime);
}

输出

HashSet 2021-08-14 11:42:43 AM
Populate set processing time: 00:00:05.6000625
Count of items: 10000000
Count processing time: 00:00:01.7703057

特殊HashSet测试:

public void TestLoadingHashSet()
{
    int length = 20000000;
    var array = new string[length];
    for (int i = 0; i < length; i++)
    {
       array[i] = i.ToString();
    }
    var dateTime = DateTime.Now;
    var hashSet = new HashSet<string>(array);
    Write("Time to load hashset: ");
    WriteLine(DateTime.Now - dateTime);
}
> TestLoadingHashSet()
Time to load hashset: 00:00:01.1918160

使用.Contains

public void TestContains()
{
    WriteLine($"Contains {DateTime.Now}");
    int length = 20000000;
    var dateTime = DateTime.Now;
    var array = new string[length];
    for (int i = 0; i < length; i++)
    {
        array[i] = i.ToString();
    }
    Write("Populate set processing time: ");
    WriteLine(DateTime.Now - dateTime);
    var newArray = new string[length/2];
    int j = 0;
    for (int i = 0; i < length; i+=2)
    {
        newArray[j++] = i.ToString();
    }
    dateTime = DateTime.Now;
    WriteLine(dateTime);
    Write("Count of items: ");
    WriteLine(array.Where(a => !newArray.Contains(a)).Count());
    Write("Count processing time: ");
    WriteLine(DateTime.Now - dateTime);
}

输出

Contains 2021-08-14 11:19:44 AM
Populate set processing time: 00:00:03.1046998
2021-08-14 11:19:49 AM
Count of items: Hosting process exited with exit code 1.
(Didnt complete. Killed it after 14 minutes)

结论:

Linq Except在我的设备上运行大约比使用HashSets慢1秒(n=20,000,000)。 使用Where和Contains运行了很长时间

哈希集的总结:

独特的数据 确保为类类型重写GetHashCode(正确地) 如果您复制数据集，可能需要高达2倍的内存，这取决于实现 HashSet是为使用IEnumerable构造函数克隆其他HashSet而优化的，但是将其他集合转换为HashSet比较慢(参见上面的特殊测试)

一行:

var list1 = new List<int> { 1, 2, 3 };
var list2 = new List<int> { 1, 2, 3, 4 };
if (list1.Except(list2).Count() + list2.Except(list1).Count() == 0)
    Console.WriteLine("same sets");

不是针对这个问题，但是这里有一些代码来比较相等和不相等的列表!相同的对象:

public class EquatableList<T> : List<T>, IEquatable<EquatableList<T>> where    T : IEquatable<T>

/// <summary>
/// True, if this contains element with equal property-values
/// </summary>
/// <param name="element">element of Type T</param>
/// <returns>True, if this contains element</returns>
public new Boolean Contains(T element)
{
    return this.Any(t => t.Equals(element));
}

/// <summary>
/// True, if list is equal to this
/// </summary>
/// <param name="list">list</param>
/// <returns>True, if instance equals list</returns>
public Boolean Equals(EquatableList<T> list)
{
    if (list == null) return false;
    return this.All(list.Contains) && list.All(this.Contains);
}