{"id":1690,"date":"2023-04-24T15:14:10","date_gmt":"2023-04-24T08:14:10","guid":{"rendered":"https:\/\/csharptutorial.net\/?page_id=1690"},"modified":"2023-05-13T14:39:28","modified_gmt":"2023-05-13T07:39:28","slug":"csharp-template-method-pattern","status":"publish","type":"page","link":"https:\/\/www.csharptutorial.net\/csharp-design-patterns\/csharp-template-method-pattern\/","title":{"rendered":"C# Template Method Pattern"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn about the Template Method pattern and how to implement it in C#.<\/p>\n\n\n\n

Introduction to the C# Template Method Pattern<\/h2>\n\n\n\n

The Template Method pattern defines a skeleton of an algorithm in a superclass and allows subclasses to redefine specific steps of the algorithm without changing its structure.<\/p>\n\n\n\n

The following UML diagram illustrates the Template Method pattern:<\/p>\n\n\n

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

Typically, the Template Method consists of an abstract class<\/a> that defines the structure of the algorithm and concrete subclasses that implement the specific steps of the algorithm. <\/p>\n\n\n\n

The abstract class provides a set of template methods that the subclasses can override to provide their own implementation.<\/p>\n\n\n\n

In practice, you use the Template Method pattern when you have an algorithm that you need to implement in a similar way across multiple classes but with some slight variations. <\/p>\n\n\n\n

Instead of duplicating the same code across different classes, you can define a standard template in a superclass, and then override some methods in the subclasses to customize the corresponding algorithm steps.<\/p>\n\n\n\n

The Template Method pattern reduces code duplication, increases code reuse, and makes it easier to maintain and modify the algorithm in the future.<\/p>\n\n\n\n

C# Template Method pattern example<\/h2>\n\n\n\n

The following program demonstrates how to use the Template Method pattern to define a generic algorithm for reading data from a file, transforming it, and storing it in a database while allowing subclasses to override specific steps to handle different file formats and database types:<\/p>\n\n\n

namespace<\/span> TemplateMethodPattern<\/span>;\n\n\n\/\/ Abstract class that defines the template method<\/span>\n\/\/ and its steps<\/span>\npublic<\/span> abstract<\/span> class<\/span> ETL<\/span>\n{\n    public<\/span> void<\/span> ImportData<\/span>(string<\/span> filename<\/span>)<\/span>\n    {\n        \/\/ Step 1: read data from file<\/span>\n        var<\/span> data = Extract(filename);\n\n        \/\/ Step 2: transform data<\/span>\n        var<\/span> transformedData = Transform(data);\n\n        \/\/ Step 3: store data in database<\/span>\n        Load(transformedData);\n    }\n\n    protected<\/span> abstract<\/span> string<\/span>[] Extract<\/span>(string<\/span> filename<\/span>)<\/span>;\n\n    protected<\/span> virtual<\/span> string<\/span>[] Transform<\/span>(string<\/span>[] data<\/span>)<\/span>\n    {\n        \/\/ Default implementation of transformation<\/span>\n        \/\/ that does nothing<\/span>\n        return<\/span> data;\n    }\n\n    protected<\/span> abstract<\/span> void<\/span> Load<\/span>(string<\/span>[] data<\/span>)<\/span>;\n}\n\n\/\/ Concrete subclass that handles<\/span>\n\/\/ CSV files and SQL Server database<\/span>\npublic<\/span> class<\/span> CSVToSQLServer<\/span> : ETL<\/span>\n{\n    protected<\/span> override<\/span> string<\/span>[] Extract<\/span>(string<\/span> filename<\/span>)<\/span>\n    {\n        \/\/ Read CSV file and return data as an array of strings<\/span>\n        return<\/span> File.ReadAllLines(filename);\n    }\n\n    protected<\/span> override<\/span> void<\/span> Load<\/span>(string<\/span>[] data<\/span>)<\/span>\n    {\n        \/\/ Store data in SQL Server database<\/span>\n        \/\/ Implementation omitted for brevity<\/span>\n        Console.WriteLine(\"Store Data in SQL Server\"<\/span>);\n    }\n}\n\n\/\/ Concrete subclass that handles<\/span>\n\/\/ Excel files and MySQL database<\/span>\npublic<\/span> class<\/span> ExcelToMySQL<\/span> : ETL<\/span>\n{\n    protected<\/span> override<\/span> string<\/span>[] Extract<\/span>(string<\/span> filename<\/span>)<\/span>\n    {\n        \/\/ Read Excel file and return data as an array of strings<\/span>\n        \/\/ Implementation omitted for brevity<\/span>\n        return<\/span> new<\/span> string<\/span>[] { \"1,2,3\"<\/span>, \"4,5,6\"<\/span> };\n    }\n\n    protected<\/span> override<\/span> string<\/span>[] Transform<\/span>(string<\/span>[] data<\/span>)<\/span>\n    {\n        \/\/ Transform Excel data to CSV format<\/span>\n        \/\/ Implementation omitted for brevity<\/span>\n        Console.WriteLine(\"Excel data transformed to CSV format\"<\/span>);\n        return<\/span> data;\n    }\n\n    protected<\/span> override<\/span> void<\/span> Load<\/span>(string<\/span>[] data<\/span>)<\/span>\n    {\n        \/\/ Store data in MySQL database<\/span>\n        \/\/ Implementation omitted for brevity<\/span>\n        Console.WriteLine(\"Data stored in MySQL\"<\/span>);\n    }\n}\n\npublic<\/span> class<\/span> Program<\/span>\n{\n    static<\/span> void<\/span> Main<\/span>(string<\/span>[] args<\/span>)<\/span>\n    {\n        \/\/ Import CSV data into SQL Server<\/span>\n        var<\/span> csvSqlServerImport = new<\/span> CSVToSQLServer();\n        csvSqlServerImport.ImportData(\"data.csv\"<\/span>);\n\n        \/\/ Import Excel data into MySQL<\/span>\n        var<\/span> excelMySqlImport = new<\/span> ExcelToMySQL();\n        excelMySqlImport.ImportData(\"data.xlsx\"<\/span>);\n\n    }\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
How it works.<\/p>\n\n\n\n
First, define an abstract class called ETL<\/code> (Extract, Transform, Load) that contains the template method called ImportData<\/code>. <\/p>\n\n\n\n
The ImportData<\/code> method defines the steps to import data from a file, transform the data, and load it into a database.<\/p>\n\n\n\n
The ImportData<\/code> method calls three abstract methods, Extract<\/code>, Transform<\/code>, and Load<\/code>, which represent the specific steps of the ETL process:<\/p>\n\n\n\n