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This article will explain in detail what the comparison methods of List objects are, and the editor thinks it is very practical, so I share it with you for reference. I hope you can get something after reading this article.

Requirement description

In the process of development, we often need to compare the data of two List objects to find out new, deleted, and changed entries. In typical cases, according to the request list given by the front end, compare it with the current records in the back table, and then add, delete and change the back table. To this end, the following example summarizes the comparison method of List objects.

Create a new console program

Create a new console program as an example.

Define a class public class Class1 {public string Id {get; set;} public string Res {get; set that records data entries }} build two List objects List listA = new List {Id = "1001", Res = "A1"}, new Class1 {Id = "1002", Res = "A2"}, new Class1 {Id = "1003", Res = "A3"}} List listB = new List {new Class1 {Id = "1001", Res = "B1"}, new Class1 {Id = "1002", Res = "B2"}, new Class1 {Id = "1004", Res = "B3"}, new Class1 {Id = "1005", Res = "B4"},} Compare two List object entries / / find out the new var queryInsert = listB.Where (b = > {if (! listA.Any (a = > a.Id = b.Id)) return true; return false;} relative to listA in listB. ToList (); queryInsert.ForEach (Q = > {WriteLine ("additions:" + q.Id + "," + q.Res);}); WriteLine () / / find var queryDelete = listA.Where (a = > {if (listB.All (b = > b.Id! = a.Id)) return true; return false;}) deleted relative to listB in listA. ToList (); queryDelete.ForEach (Q = > {WriteLine ("deleted items:" + q.Id + "," + q.Res);}); WriteLine () / / find out the relative listA updated var queryUpdate = listB.Where (b = > {if (listA.Any (a = > a.Id = = b.Id)) return true; return false;} from listB. ToList (); queryUpdate.ForEach (Q = > {WriteLine ("update items:" + q.Id + "," + q.Res);}); output the result

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