{"id":1473,"date":"2023-04-10T12:25:57","date_gmt":"2023-04-10T05:25:57","guid":{"rendered":"https:\/\/csharptutorial.net\/?page_id=1473"},"modified":"2024-12-14T22:47:28","modified_gmt":"2024-12-14T15:47:28","slug":"csharp-dependency-inversion-principle","status":"publish","type":"page","link":"https:\/\/www.csharptutorial.net\/csharp-design-patterns\/csharp-dependency-inversion-principle\/","title":{"rendered":"C# Dependency Inversion Principle"},"content":{"rendered":"\n<p><strong>Summary<\/strong>: in this tutorial, you&#8217;ll learn about the C# Dependency Inversion Principle that promotes the decoupling of software modules.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Introduction to the C# Dependency Inversion Principle<\/h2>\n\n\n\n<p>The Dependency Inversion Principle (DIP) is the last principle of the SOLID principles:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><a href=\"https:\/\/csharptutorial.net\/csharp-design-patterns\/csharp-single-responsibility-principle\/\">Single Responsibility Principle (SRP)<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/csharptutorial.net\/csharp-design-patterns\/csharp-open-closed-principle\/\">Open-Closed Principle (OCP)<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/csharptutorial.net\/csharp-design-patterns\/csharp-liskov-substitution-principle\/\">Liskov Substitution Principle (LSP)<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/csharptutorial.net\/csharp-design-patterns\/csharp-interface-segregation-principle\/\">Interface Segregation Principle (ISP)&nbsp;<\/a><\/li>\n\n\n\n<li><strong>Dependency Inversion Principle (DIP)<\/strong><\/li>\n<\/ul>\n\n\n\n<p>The Dependency Inversion Principle states that high-level modules should not depend on low-level modules, but both should depend on abstractions.<\/p>\n\n\n\n<p>To understand the Dependency Inversion Principle, you first need to understand the concepts of high-level and low-level modules.<\/p>\n\n\n\n<p>Generally, high-level modules contain the main logic of the application, while low-level modules provide supporting functionality. In other words, high-level modules specify what the application will do, while low-level modules specify how it will do it.<\/p>\n\n\n\n<p>Traditionally, high-level modules depend on low-level modules, as the low-level modules provide the necessary functionality that high-level modules require. However, this creates a tight coupling between the two modules. If you change one more, it likely affects the other.<\/p>\n\n\n\n<p>The Dependency Inversion Principle solves this problem by introducing an abstraction layer between the high-level and low-level modules.<\/p>\n\n\n\n<p>This abstraction layer is represented by an interface, which defines the methods that the low-level module must implement to provide its functionality.<\/p>\n\n\n\n<p>The high-level module depends on this interface instead of the low-level module. In other words, the Dependency Inversion Principle promotes the decoupling of software modules.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">C# Dependency Inversion Principle example<\/h2>\n\n\n\n<p>The following example is an illustration of violating the dependency inversion principle:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-1\" data-shcb-language-name=\"C#\" data-shcb-language-slug=\"cs\"><span><code class=\"hljs language-cs\"><span class=\"hljs-keyword\">namespace<\/span> <span class=\"hljs-title\">DIP<\/span>;\n\n<span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title\">DatabaseService<\/span>\n{\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title\">Save<\/span>(<span class=\"hljs-params\"><span class=\"hljs-keyword\">string<\/span> message<\/span>)<\/span>\n    {\n        Console.WriteLine(<span class=\"hljs-string\">\"Save the message into the database\"<\/span>);\n    }\n}\n<span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title\">Logger<\/span>\n{\n    <span class=\"hljs-keyword\">private<\/span> <span class=\"hljs-keyword\">readonly<\/span> DatabaseService _databaseService;\n\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-title\">Logger<\/span>(<span class=\"hljs-params\">DatabaseService databaseService<\/span>)<\/span>\n    {\n        _databaseService = databaseService;\n    }\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title\">Log<\/span>(<span class=\"hljs-params\"><span class=\"hljs-keyword\">string<\/span> message<\/span>)<\/span>\n    {\n        _databaseService.Save(message);\n    }\n}\n\n<span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title\">Program<\/span>\n{\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">static<\/span> <span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title\">Main<\/span>(<span class=\"hljs-params\"><span class=\"hljs-keyword\">string<\/span>&#91;] args<\/span>)<\/span>\n    {\n        <span class=\"hljs-keyword\">var<\/span> logger = <span class=\"hljs-keyword\">new<\/span> Logger(<span class=\"hljs-keyword\">new<\/span> DatabaseService());\n        logger.Log(<span class=\"hljs-string\">\"Hello\"<\/span>);\n    }\n}\n<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-1\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">C#<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">cs<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>In this example, we have two main classes <code>DatabaseService<\/code> and <code>Logger<\/code>: <\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The <code>DatabaseService<\/code> is a low-level module that provides database access.<\/li>\n\n\n\n<li>The <code>Logger<\/code> is a high-level module that logs data.<\/li>\n<\/ul>\n\n\n\n<p>The <code>Logger<\/code> class depends on <code>DatabaseService<\/code> class directly. In other words, the high-level module (<code>Logger<\/code>) depends on the low-level module (<code>DatabaseService<\/code>).<\/p>\n\n\n\n<p>Rather than having the <code>Logger<\/code> class depends on the <code>DatabaseService<\/code> class, we can introduce an interface called <code>IDataService<\/code> that both classes depend on:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-2\" data-shcb-language-name=\"C#\" data-shcb-language-slug=\"cs\"><span><code class=\"hljs language-cs\"><span class=\"hljs-keyword\">namespace<\/span> <span class=\"hljs-title\">DIP<\/span>;\n\n<span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">interface<\/span> <span class=\"hljs-title\">IDataService<\/span>\n{\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title\">Save<\/span>(<span class=\"hljs-params\"><span class=\"hljs-keyword\">string<\/span> message<\/span>)<\/span>;\n}\n\n<span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title\">DatabaseService<\/span>: <span class=\"hljs-title\">IDataService<\/span>\n{\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title\">Save<\/span>(<span class=\"hljs-params\"><span class=\"hljs-keyword\">string<\/span> message<\/span>)<\/span>\n    {\n        Console.WriteLine(<span class=\"hljs-string\">\"Save the message into the database\"<\/span>);\n    }\n}\n\n<span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title\">Logger<\/span>\n{\n    <span class=\"hljs-keyword\">private<\/span> <span class=\"hljs-keyword\">readonly<\/span> IDataService _dataService;\n\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-title\">Logger<\/span>(<span class=\"hljs-params\">IDataService dataService<\/span>)<\/span>\n    {\n        _dataService = dataService;\n    }\n\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title\">Log<\/span>(<span class=\"hljs-params\"><span class=\"hljs-keyword\">string<\/span> message<\/span>)<\/span>\n    {\n        _dataService.Save(message);\n    }\n}\n\n<span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title\">Program<\/span>\n{\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">static<\/span> <span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title\">Main<\/span>(<span class=\"hljs-params\"><span class=\"hljs-keyword\">string<\/span>&#91;] args<\/span>)<\/span>\n    {\n        <span class=\"hljs-keyword\">var<\/span> logger = <span class=\"hljs-keyword\">new<\/span> Logger(<span class=\"hljs-keyword\">new<\/span> DatabaseService());\n        logger.Log(<span class=\"hljs-string\">\"Hello\"<\/span>);\n    }\n}<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-2\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">C#<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">cs<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>In this example:<\/p>\n\n\n\n<p>First, define the <code>IDataAccess<\/code> interface that has the <code>Save()<\/code> method:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-3\" data-shcb-language-name=\"C#\" data-shcb-language-slug=\"cs\"><span><code class=\"hljs language-cs\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">interface<\/span> <span class=\"hljs-title\">IDataService<\/span>\n{\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title\">Save<\/span>(<span class=\"hljs-params\"><span class=\"hljs-keyword\">string<\/span> message<\/span>)<\/span>;\n}<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-3\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">C#<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">cs<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Second, redefine the <code>DatabaseAccess<\/code> that implements the <code>IDataAccess<\/code> interface:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-4\" data-shcb-language-name=\"C#\" data-shcb-language-slug=\"cs\"><span><code class=\"hljs language-cs\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title\">DatabaseService<\/span>: <span class=\"hljs-title\">IDataService<\/span>\n{\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title\">Save<\/span>(<span class=\"hljs-params\"><span class=\"hljs-keyword\">string<\/span> message<\/span>)<\/span>\n    {\n        Console.WriteLine(<span class=\"hljs-string\">\"Save the message into the database\"<\/span>);\n    }\n}<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-4\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">C#<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">cs<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Third, change the member and constructor of the <code>Logger<\/code> class to use the <code>IDataAccess<\/code> interface instead of the <code>DatabaseAccess<\/code> class:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-5\" data-shcb-language-name=\"C#\" data-shcb-language-slug=\"cs\"><span><code class=\"hljs language-cs\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title\">Logger<\/span>\n{\n    <span class=\"hljs-keyword\">private<\/span> <span class=\"hljs-keyword\">readonly<\/span> IDataService _dataService;\n\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-title\">Logger<\/span>(<span class=\"hljs-params\">IDataService dataService<\/span>)<\/span>\n    {\n        _dataService = dataService;\n    }\n\n    <span class=\"hljs-function\"><span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title\">Log<\/span>(<span class=\"hljs-params\"><span class=\"hljs-keyword\">string<\/span> message<\/span>)<\/span>\n    {\n        _dataService.Save(message);\n    }\n}<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-5\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">C#<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">cs<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>By doing this, we can decouple the <code>Logger<\/code> and <code>DatabaseService<\/code> classes, making it easier to change one class without affecting each other.<\/p>\n\n\n\n<p>Also, we can easily swap the <code>DatabaseService<\/code> class for a different class that implements the <code>IDataService<\/code> interface. For example, we can define  <code>FileService<\/code> class that saves a message into a text file by passing it to the <code>Logger<\/code> class.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Summary<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The Dependency Inversion Principle states that high-level modules should not depend on low-level modules, but both should depend on abstractions.<\/li>\n<\/ul>\n<div class=\"helpful-block-content\" data-title=\"\">\n\t<header>\n\t\t<div class=\"wth-question\">Was this tutorial helpful ?<\/div>\n\t\t<div class=\"wth-thumbs\">\n\t\t\t<button\n\t\t\t\tdata-post=\"1473\"\n\t\t\t\tdata-post-url=\"https:\/\/www.csharptutorial.net\/csharp-design-patterns\/csharp-dependency-inversion-principle\/\"\n\t\t\t\tdata-post-title=\"C# Dependency Inversion Principle\"\n\t\t\t\tdata-response=\"1\"\n\t\t\t\tclass=\"wth-btn-rounded wth-yes-btn\"\n\t\t\t>\n\t\t\t\t<svg\n\t\t\t\t\txmlns=\"http:\/\/www.w3.org\/2000\/svg\"\n\t\t\t\t\tviewBox=\"0 0 24 24\"\n\t\t\t\t\tfill=\"none\"\n\t\t\t\t\tstroke=\"currentColor\"\n\t\t\t\t\tstroke-width=\"2\"\n\t\t\t\t\tstroke-linecap=\"round\"\n\t\t\t\t\tstroke-linejoin=\"round\"\n\t\t\t\t\tclass=\"feather feather-thumbs-up block w-full h-full\"\n\t\t\t\t>\n\t\t\t\t\t<path\n\t\t\t\t\t\td=\"M14 9V5a3 3 0 0 0-3-3l-4 9v11h11.28a2 2 0 0 0 2-1.7l1.38-9a2 2 0 0 0-2-2.3zM7 22H4a2 2 0 0 1-2-2v-7a2 2 0 0 1 2-2h3\"\n\t\t\t\t\t><\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t<span class=\"sr-only\"> Yes <\/span>\n\t\t\t<\/button>\n\n\t\t\t<button\n\t\t\t\tdata-response=\"0\"\n\t\t\t\tdata-post=\"1473\"\n\t\t\t\tdata-post-url=\"https:\/\/www.csharptutorial.net\/csharp-design-patterns\/csharp-dependency-inversion-principle\/\"\n\t\t\t\tdata-post-title=\"C# Dependency Inversion Principle\"\n\t\t\t\tclass=\"wth-btn-rounded wth-no-btn\"\n\t\t\t>\n\t\t\t\t<svg\n\t\t\t\t\txmlns=\"http:\/\/www.w3.org\/2000\/svg\"\n\t\t\t\t\tviewBox=\"0 0 24 24\"\n\t\t\t\t\tfill=\"none\"\n\t\t\t\t\tstroke=\"currentColor\"\n\t\t\t\t\tstroke-width=\"2\"\n\t\t\t\t\tstroke-linecap=\"round\"\n\t\t\t\t\tstroke-linejoin=\"round\"\n\t\t\t\t>\n\t\t\t\t\t<path\n\t\t\t\t\t\td=\"M10 15v4a3 3 0 0 0 3 3l4-9V2H5.72a2 2 0 0 0-2 1.7l-1.38 9a2 2 0 0 0 2 2.3zm7-13h2.67A2.31 2.31 0 0 1 22 4v7a2.31 2.31 0 0 1-2.33 2H17\"\n\t\t\t\t\t><\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t<span class=\"sr-only\"> No <\/span>\n\t\t\t<\/button>\n\t\t<\/div>\n\t<\/header>\n\n\t<div class=\"wth-form hidden\">\n\t\t<div class=\"wth-form-wrapper\">\n\t\t\t<div class=\"wth-title\"><\/div>\n\t\t\t\n\t\t\t<textarea class=\"wth-message\"><\/textarea>\n\n\t\t\t<button class=\"btn btn-primary wth-btn-submit\">Send<\/button>\n\t\t\t<button class=\"btn wth-btn-cancel\">Cancel<\/button>\n\t\t\n\t\t<\/div>\n\t<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>In this tutorial, you&#8217;ll learn about the C# Dependency Inversion Principle that promotes the decoupling of software modules.<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1441,"menu_order":4,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1473","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/pages\/1473","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/comments?post=1473"}],"version-history":[{"count":4,"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/pages\/1473\/revisions"}],"predecessor-version":[{"id":2711,"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/pages\/1473\/revisions\/2711"}],"up":[{"embeddable":true,"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/pages\/1441"}],"wp:attachment":[{"href":"https:\/\/www.csharptutorial.net\/wp-json\/wp\/v2\/media?parent=1473"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}