如何比较两个列表，ASP.net

Question

I have two list and wanna know which items are in the fist one and arn't in second one,

List<int> viewphonenumid = new List<int>();
List<int?> DtoPhonenumId = new List<int?>();

For instance viewphonenumid has {1,2,3,4,5,6} and DtoPhonenumId has{3,4,5,6} and I wanna have {1,2} in a new list.

Answer 1

var newList= viewphonenumid.Except(DtoPhonenumId).ToList();

You also can specify comparer.

http://msdn.microsoft.com/library/bb336390(v=vs.110).aspx

Answer 2

也许是这样的：

var newList= viewphonenumid.Where(v =>! DtoPhonenumId.Contains(v)).ToList();

Answer 3

I suggest you to use Enumerable.Except http://msdn.microsoft.com/ru-ru/library/bb300779(v=vs.110).aspx

Something like this

(new List<int> {1,2,3,4}).Except(new List<int> {3,4})

Answer 4

try following:

List<int> result = new List<int>();
foreach(int element in viewphonenumid)
    if(!DtoPhonenumId.Contains(element))
        result.Add(element);

I hope that help

Answer 5

If you want to compare two list of items in C#, You should use Enumerable.SequenceEqual method.

List<int> list1 = new List<int>();

list1.Add(7);
list1.Add(5);
list1.Add(9);

List<int> list2 = new List<int>();

list2.Add(7);
list2.Add(5);
list2.Add(9);

if (list1.SequenceEqual(list2))
{
     //lists are identical
}
else
{
     // lists have different items
}

LINQ has a pretty good algorithm for that.