在C＃中通过LINQ比较两个列表？

Question

if (!list.SequenceEqual(new TESTList()))
{
     MessageBox.Show("updated");
}

Pretty much this code does not seem to work.

I have a class as so;

class TESTList
{
private bool test;
}

Now, assuming my code all works and list is properly created, how can I determine if the two lists are the same by checking each item in the list (its boolean) and determing overall taht if both items (ex. item1 list1 and item1 list2) have same booleans, then both lists same.

I don't know.

Answer 1

Be careful with Enumerable.Zip recommendation as it can result in true where the 2 input sequences are of different lengths but match up to the point where the shorter sequence ends. It will even result in true if one of the sequences is empty and the other is not!

result here will be true :

var list1 = new List<int> { 1, 2, 3 };
var list2 = new List<int> { 1, 2, 3, 4 };

bool result = Enumerable.Zip(list1, list2, (left, right) => left == right).All(x => x);

---

Instead you might want to use SequenceEqual :

bool result = list1.SequenceEqual(list2);

Results:

var list1 = new List<int> { 1, 2, 3 };
var list2 = new List<int> { 1, 2, 3 };

TRUE

var list1 = new List<int> { 1, 2, 3 };
var list2 = new List<int> { 1, 2, 3, 4 };

FALSE

If you require a result of true when the sequences contain the same elements in any order you need to sort both sequences before comparing them:

bool result = list1.OrderBy (l => l).SequenceEqual(list2.OrderBy (l => l));

You should note that SequenceEqual uses the default equality comparer for the type inside the list. This will work out of the box for a bool but you may need to override Equals if your list contains a custom class which is only differentiated by a private field (I suspect your final code won't really look like that).

Answer 2

bool result = Enumerable.Zip(list1, list2, (left, right) => left == right).All(x => x);

Answer 3

Given that this is a custom class (and what's more, the test field is private), there's no possible way as written for LINQ to check equality properly, so it would need to fall back on reference-equality, where the same memory addresses are being pointed to by each list. There's no particular reason to suppose this to be the case.

You'll need to implement a custom Equals method in TESTlist , therefore. (Untested.)

  public overrides bool Equals(object other) {
    var tlo = other as TESTlist;
    if (tlo != null) {
      return tlo.test == this.test;
    }
    else {
      return false;     // It's not a TESTlist, it can't be equal
    }
  }