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Editor to share with you how to write LINQ expressions, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's learn about it!

Introduction to LINQ expression

Beyond 1.OO (object oriented): access and integration of information. Relational database and XML are typical applications.

2.NET Language Integrated Query (LINQ): instead of using proprietary solutions specific to relational databases or XML, general solutions are used to solve the problems of access and integration of various information sources.

3. In LINQ, query has become a part of programming language, which makes query expressions get the benefits of strongly typed languages such as compile-time syntax checking, rich metadata, intelligence awareness and so on.

Knowing LINQ expression for the first time

Class app {static void Main () {string [] names = {"Burke", "Connor", "Frank", "Everett", "Albert", "George", "Harris", "David"}; IEnumerable query = from s in names where s.Length = = 5 orderby s select s.ToUpper (); foreach (string item in query) Console.WriteLine (item);}}

Parsing of LINQ expression

IEnumerable query = from s in names where s.Length = = 5 orderby s select s.ToUpper ()

Semantically equivalent to the following "method-style (method-based) query":

IEnumerable query = names .Where (s = > s.Length = = 5) .OrderBy (s = > s) .Select (s = > s.ToUpper ())

Parsing of LINQ query expression

Func filter = delegate (string s) {return s.Length = = 5;}; Func extract = delegate (string s) {return s;}; Func project = delegate (string s) {return s.ToUpper ();}; IEnumerable query = names.Where (filter) .OrderBy (extract) .Select (project)

Analysis of query operator and extension method

Query operators are another important facility in LINQ, and LINQ uses extension methods to define query operators, such as the where operator:

Namespace System.Linq {public static class Enumerable {public static IEnumerable Where (this IEnumerable source, Func predicate) {foreach (T item in source) if (predicate (item)) yield return item;} above is all the content of this article "how to write LINQ expressions". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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