Part 30 SequenceEqual Operator in LINQ HD

Link for all dot net and sql server video tutorial playlists http://www.youtube.com/user/kudvenkat/playlists Link for slides, code samples and text version of the video http://csharp-video-tutorials.blogspot.com/2014/08/part-30-sequenceequal-operator-in-linq.html SequenceEqual() method is used to determine whether two sequences are equal. This method returns true if the sequences are equal otherwise false. For 2 sequences to be equal 1. Both the sequences should have same number of elements and 2. Same values should be present in the same order in both the sequences Example 1 : SequenceEqual() returns true. string[] countries1 = { "USA", "India", "UK" }; string[] countries2 = { "USA", "India", "UK" }; var result = countries1.SequenceEqual(countries2); Console.WriteLine("Are Equal = " + result); Example 2 : In this case, SequenceEqual() returns false, as the default comparison is case sensitive. string[] countries1 = { "USA", "INDIA", "UK" }; string[] countries2 = { "usa", "india", "uk" }; var result = countries1.SequenceEqual(countries2); Console.WriteLine("Are Equal = " + result); Example 3: If we want the comparison to be case insensitive, then use the other overloaded version of SequenceEqual() method to which we can pass an alternate comparer. string[] countries1 = { "USA", "INDIA", "UK" }; string[] countries2 = { "usa", "india", "uk" }; var result = countries1.SequenceEqual(countries2, StringComparer.OrdinalIgnoreCase); Console.WriteLine("Are Equal = " + result); Example 4 : SequenceEqual() returns false. This is because, although both the sequences contain same data, the data is not present in the same order. string[] countries1 = { "USA", "INDIA", "UK" }; string[] countries2 = { "UK", "INDIA", "USA" }; var result = countries1.SequenceEqual(countries2); Console.WriteLine("Are Equal = " + result); Example 5 : To fix the problem in Example 4, use OrderBy() to sort data in the source sequences. string[] countries1 = { "USA", "INDIA", "UK" }; string[] countries2 = { "UK", "INDIA", "USA" }; var result = countries1.OrderBy(c =] c).SequenceEqual(countries2.OrderBy(c =] c)); Console.WriteLine("Are Equal = " + result); Example 6 : When comparing complex types, the default comparer will only check if the object references are equal. So, in this case SequenceEqual() returns false. List[Employee] list1 = new List[Employee]() { new Employee { ID = 101, Name = "Mike"}, new Employee { ID = 102, Name = "Susy"}, }; List[Employee] list2 = new List[Employee]() { new Employee { ID = 101, Name = "Mike"}, new Employee { ID = 102, Name = "Susy"}, }; var result = list1.SequenceEqual(list2); Console.WriteLine("Are Equal = " + result); To solve the problem in Example 6, there are 3 ways 1. Use the other overloaded version of SequenceEqual() 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 ano