Posts Tagged ‘extension method’
Extension method in .net
Extension methods enable developers to add a method to an existing class without deriving or affecting the existing class. This extension methods only support a sub routine or a function.
Example if we want to extend the functionality of the String type
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Imports System.Runtime.CompilerServices
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Module StringExtensions
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<Extension()>
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Public Sub Print(ByVal aString As String)
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Console.WriteLine(aString)
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End Sub
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<Extension()>
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Public Sub PrintAndPunctuate(ByVal aString As String,
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ByVal punc As String)
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Console.WriteLine(aString & punc)
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End Sub
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End Module
To use that function
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Sub Main()
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Dim example As String = "Example string"
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example.Print()
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example = "Hello"
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example.PrintAndPunctuate(".")
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example.PrintAndPunctuate("!!!!")
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End Sub
C#.NET
If you notice the parameter there is a this keyword, that is how it done.
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namespace ExtensionMethods
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{
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public static class StringExtensions
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{
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public static int Print(<strong>this </strong>String str)
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{
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Console.WriteLine(String );
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}
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}
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}
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string s = "Hello Extension Method";
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s.Print();