Difference between “Equals” and “SequenceEqual”?

Question

Is there any cases in which:

Equals(MyList1, MyList2) != MyList1.SequenceEqual(MyList2);

And what is the difference between:

Equals(obj1, obj2) and obj1.Equals(obj2)

Thanks.

Answer 1

Equals returns true only if MyList1 and MyList2 are the same instance.
SequenceEqual returns true if both lists contain the same items.

Example:

var list1 = new List<int> { 1, 2, 3 };
var list2 = new List<int> { 1, 2, 3 };
var list3 = list1;
var list4 = new List<int> { 1, 2, 3, 4 };

Equals(list1, list2) == false
list1.SequenceEqual(list2) == true

Equals(list1, list3) == true
list1.SequenceEqual(list3) == true

Equals(list1, list4) == false
list1.SequenceEqual(list4) == false

---

The difference between Equals(obj1, obj2) and obj1.Equals(obj2) is that the first one uses the static method Object.Equals and the second uses the instance method Equals. The result of these two calls will differ, if the class of obj1 overrides Object.Equals.

Answer 2

For 2nd part of question as first has been answered by @Daniel:

Equals(obj1, obj2) and obj1.Equals(obj2)

obj1.Equals(obj2) is instance method of object and it will throw exception if obj1 is null. Where as Equals(obj1,obj2) is static method and will work if you obj1 is null. You can also override Euqals for a class

object obj1 = new object();
object obj2 = new object();
Console.WriteLine(obj1.Equals(obj2)); //print false
obj1 = null;
Console.WriteLine(obj1.Equals(obj2)); // will throw exception
Console.WriteLine(Equals(obj1, obj2));// return false in this case and since its static it will not throw the exception