{"id":1740,"date":"2023-05-06T16:17:32","date_gmt":"2023-05-06T09:17:32","guid":{"rendered":"https:\/\/csharptutorial.net\/?page_id=1740"},"modified":"2023-05-13T14:53:17","modified_gmt":"2023-05-13T07:53:17","slug":"csharp-bridge-pattern","status":"publish","type":"page","link":"https:\/\/www.csharptutorial.net\/csharp-design-patterns\/csharp-bridge-pattern\/","title":{"rendered":"C# Bridge Pattern"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn about the C# Bridge pattern that decouples an abstraction from its implementation so that the two can vary independently.<\/p>\n\n\n\n

Introduction to the C# Bridge pattern<\/h2>\n\n\n\n

By definition, a Bridge pattern allows you to decouple an abstraction from its implementation so that you can change the two independently.<\/p>\n\n\n\n

Suppose you have the following shape class hierarchy:<\/p>\n\n\n

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\"C#<\/figure>\n<\/div>\n\n\n

To make both triangles and rectangles rounded and sketched, you may end up with the subclasses of the Triangle<\/code> and Rectangle<\/code> classes like this:<\/p>\n\n\n

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\"C#<\/figure>\n<\/div>\n\n\n

But this approach is not flexible because inheritance<\/a> binds a style (implementation) to a shape (abstraction) permanently. <\/p>\n\n\n\n

For example, if you want to add a new shape like a pentagon, you need to define three classes Pentagon<\/code>, RoundedPentagon<\/code>, and SketchedPentagon<\/code>.<\/p>\n\n\n\n

Additionally, if you want to add a more shape style like embossed, you need to add a new class to each shape, which does not scale well.<\/p>\n\n\n\n

To solve this problem, you can use the Bridge pattern to separate the style from the shape hierarchy like this:<\/p>\n\n\n

\n
\"C#<\/figure>\n<\/div>\n\n\n

C# Bridge pattern implementation<\/h2>\n\n\n\n

The following program illustrates the bridge pattern:<\/p>\n\n\n

using<\/span> static<\/span> System.Console;\n\nnamespace<\/span> BridgePattern<\/span>;\n\npublic<\/span> abstract<\/span> class<\/span> Style<\/span>\n{\n    public<\/span> abstract<\/span> void<\/span> Decorate<\/span>(<\/span>)<\/span>;\n}\n\npublic<\/span> class<\/span> RoundedStyle<\/span> : Style<\/span>\n{\n    public<\/span> override<\/span> void<\/span> Decorate<\/span>(<\/span>)<\/span> => WriteLine(\"rounded.\"<\/span>);\n}\n\npublic<\/span> class<\/span> SketchedStyle<\/span> : Style<\/span>\n{\n    public<\/span> override<\/span> void<\/span> Decorate<\/span>(<\/span>)<\/span> => WriteLine(\"sketched.\"<\/span>);\n}\n\npublic<\/span> abstract<\/span> class<\/span> Shape<\/span>\n{\n    protected<\/span> Style Style;\n\n    public<\/span> Shape<\/span>(Style style<\/span>)<\/span>\n    {\n        Style = style;\n    }\n\n    public<\/span> abstract<\/span> void<\/span> ApplyStyle<\/span>(<\/span>)<\/span>;\n\n}\n\npublic<\/span> class<\/span> Triangle<\/span> : Shape<\/span>\n{\n    public<\/span> Triangle<\/span>(Style style<\/span>) : base<\/span>(style<\/span>)<\/span>\n    {\n    }\n\n    public<\/span> override<\/span> void<\/span> ApplyStyle<\/span>(<\/span>)<\/span>\n    {\n        Write(\"Make the triangle \"<\/span>);\n        Style.Decorate();\n    }\n}\n\npublic<\/span> class<\/span> Rectangle<\/span> : Shape<\/span>\n{\n    public<\/span> Rectangle<\/span>(Style style<\/span>) : base<\/span>(style<\/span>)<\/span>\n    {\n    }\n\n    public<\/span> override<\/span> void<\/span> ApplyStyle<\/span>(<\/span>)<\/span>\n    {\n        Write(\"Make the rectangle \"<\/span>);\n        Style.Decorate();\n    }\n}\npublic<\/span> class<\/span> Program<\/span>\n{\n    public<\/span> static<\/span> void<\/span> Main<\/span>(string<\/span>[] args<\/span>)<\/span>\n    {\n        var<\/span> triangle = new<\/span> Triangle(new<\/span> SketchedStyle());\n        triangle.ApplyStyle();\n\n        var<\/span> rectangle = new<\/span> Rectangle(new<\/span> RoundedStyle());\n        rectangle.ApplyStyle();\n    }\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Make the triangle sketched.\r\nMake the rectangle rounded.<\/code><\/span><\/pre>\n\n\n
How it works.<\/p>\n\n\n\n
First, define the Style<\/code> abstract class<\/a> that has the Decorate()<\/code> abstract method:<\/p>\n\n\n
public<\/span> abstract<\/span> class<\/span> Style<\/span>\n{\n    public<\/span> abstract<\/span> void<\/span> Decorate<\/span>(<\/span>)<\/span>;\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Second, define the RoundedStyle<\/code> class that inherits from the Style<\/code> class. The Decorate()<\/code> method displays the \" rounded.\"<\/code> message to the Console:<\/p>\n\n\n
public<\/span> class<\/span> RoundedStyle<\/span> : Style<\/span>\n{\n    public<\/span> override<\/span> void<\/span> Decorate<\/span>(<\/span>)<\/span> => WriteLine(\"rounded.\"<\/span>);\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Third, define the SketchedStyle<\/code> class that also inherits from the Style<\/code> class. The Decorate()<\/code> method shows the \" sketched.\"<\/code> message to the Console:<\/p>\n\n\n
public<\/span> class<\/span> SketchedStyle<\/span> : Style<\/span>\n{\n    public<\/span> override<\/span> void<\/span> Decorate<\/span>(<\/span>)<\/span> => WriteLine(\"sketched.\"<\/span>);\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Fourth, define the Shape<\/code> abstract class that has a Style<\/code> object as a property and an abstract method ApplyStyle()<\/code> that calls the Decorate()<\/code> method of the Style<\/code> object to set the style for shape:<\/p>\n\n\n
public<\/span> abstract<\/span> class<\/span> Shape<\/span>\n{\n\n    protected<\/span> Style Style;\n\n    public<\/span> Shape<\/span>(Style style<\/span>)<\/span>\n    {\n        Style = style;\n    }\n\n    public<\/span> abstract<\/span> void<\/span> ApplyStyle<\/span>(<\/span>)<\/span>;\n\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Fifth, define the Triangle<\/code> class that extends the Shape<\/code> class. The ApplyStyle()<\/code> method writes a message to the console and calls the Decorate()<\/code> method of the style object:<\/p>\n\n\n
public<\/span> class<\/span> Triangle<\/span> : Shape<\/span>\n{\n    public<\/span> Triangle<\/span>(Style style<\/span>) : base<\/span>(style<\/span>)<\/span>\n    {\n    }\n\n    public<\/span> override<\/span> void<\/span> ApplyStyle<\/span>(<\/span>)<\/span>\n    {\n        Write(\"Make the triangle \"<\/span>);\n        Style.Decorate();\n    }\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Sixth, define the Rectangle<\/code> class that inherits from the Shape<\/code> class. The ApplyStyle()<\/code> method also writes a message to the console and calls the Decorate()<\/code> method of the Style<\/code> object:<\/p>\n\n\n
public<\/span> class<\/span> Rectangle<\/span> : Shape<\/span>\n{\n    public<\/span> Rectangle<\/span>(Style style<\/span>) : base<\/span>(style<\/span>)<\/span>\n    {\n    }\n\n    public<\/span> override<\/span> void<\/span> ApplyStyle<\/span>(<\/span>)<\/span>\n    {\n        Write(\"Make the rectangle \"<\/span>);\n        Style.Decorate();\n    }\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Finally, create an instance of the Triangle<\/code> class with the SketchedStyle<\/code> and calls the ApplyStyle()<\/code><\/code> method to set its style to sketch. Similarly, create an instance of the Rectangle<\/code> class and calls the ApplyStyle()<\/code><\/code> method to set its style to rounded.<\/p>\n\n\n
public<\/span> class<\/span> Program<\/span>\n{\n    public<\/span> static<\/span> void<\/span> Main<\/span>(string<\/span>[] args<\/span>)<\/span>\n    {\n        var<\/span> triangle = new<\/span> Triangle(new<\/span> SketchedStyle());\n        triangle.ApplyStyle();\n\n        var<\/span> rectangle = new<\/span> Rectangle(new<\/span> RoundedStyle());\n        rectangle.ApplyStyle();\n    }\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Summary<\/h2>\n\n\n\n
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  • Use the C# Bridge pattern to decouple an abstraction from its implementation so that the two can vary independently.<\/li>\n<\/ul>\n
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