Part 27 Union, Intersect and Except operators in LINQ

Text version of the video http://csharp-video-tutorials.blogspot.com/2014/08/part-27-union-intersect-and-except.html Healthy diet is very important both for the body and mind. If you like Aarvi Kitchen recipes, please support by sharing, subscribing and liking our YouTube channel. Hope you can help. https://www.youtube.com/channel/UC7sEwIXM_YfAMyonQCrGfWA/?sub_confirmation=1 Slides http://csharp-video-tutorials.blogspot.com/2014/08/part-27-union-intersect-and-except_11.html LINQ Tutorial - All Text Articles & Slides http://csharp-video-tutorials.blogspot.com/2014/07/linq-tutorial.html LINQ Tutorial Playlist https://www.youtube.com/playlist?list=PL6n9fhu94yhWi8K02Eqxp3Xyh_OmQ0Rp6 Dot Net, SQL, Angular, JavaScript, jQuery and Bootstrap complete courses https://www.youtube.com/user/kudvenkat/playlists?view=1&sort=dd The following operators belong to Set operators category Distinct Union Intersect Except We discussed Distinct operator in Part 26. In this video we will discuss Union, Intersect and Except operators. Union combines two collections into one collection while removing the duplicate elements. Example 1: numbers1 and numbers2 collections are combined into a single collection. Notice that, the duplicate elements are removed. int[] numbers1 = { 1, 2, 3, 4, 5 }; int[] numbers2 = { 1, 3, 6, 7, 8 }; var result = numbers1.Union(numbers2); foreach (var v in result) { Console.WriteLine(v); } When comparing elements, just like Distinct() method, Union(), Intersect() and Except() methods work in a slightly different manner with complex types like Employee, Customer etc. Example 2 : Notice that in the output the duplicate employee objects are not removed. This is because, the default comparer is being used which will just check for object references being equal and not the individual property values. List[Employee] list1 = new List[Employee]() { new Employee { ID = 101, Name = "Mike"}, new Employee { ID = 102, Name = "Susy"}, new Employee { ID = 103, Name = "Mary"} }; List[Employee] list2 = new List[Employee]() { new Employee { ID = 101, Name = "Mike"}, new Employee { ID = 104, Name = "John"} }; var result = list1.Union(list2); foreach (var v in result) { Console.WriteLine(v.ID + "\t" + v.Name); } Example 3 : To solve the problem in Example 2, there are 3 ways 1. Use the other overloaded version of Union() method to which we can pass a custom class that implements IEqualityComparer 2. Override Equals() and GetHashCode() methods in Employee class 3. Project the properties into a new anonymous type, which overrides Equals() and GetHashCode() methods Project the properties into a new anonymous type, which overrides Equals() and GetHashCode() methods List[Employee] list1 = new List[Employee]() { new Employee { ID = 101, Name = "Mike"}, new Employee { ID = 102, Name = "Susy"}, new Employee { ID = 103, Name = "Mary"} }; List[Employee] list2 = new List[Employee]() { new Employee { ID = 101, Name = "Mike"}, new Employee { ID = 104, Name = "John"} }; var result = list1.Select(x =] new { x.ID, x.Name }).Union(list2.Select(x =] new { x.ID, x.Name })); foreach (var v in result) { Console.WriteLine(v.ID + "\t" + v.Name); } Intersect() returns the common elements between the 2 collections. Example 4 : Return common elements in numbers1 and numbers2 collections. int[] numbers1 = { 1, 2, 3, 4, 5 }; int[] numbers2 = { 1, 3, 6, 7, 8 }; var result = numbers1.Intersect(numbers2); foreach (var v in result) { Console.WriteLine(v); } Except() returns the elements that are present in the first collection but not in the second collection. Example 5: Return the elements that are present in the first collection but not in the second collection. int[] numbers1 = { 1, 2, 3, 4, 5 }; int[] numbers2 = { 1, 3, 6, 7, 8 }; var result = numbers1.Except(numbers2); foreach (var v in result) { Console.WriteLine(v); }