Extension Methods without 3.5 Framework

MSDN Blog Postings » Extension Methods without 3.5 Framework

MSDN Blog Postings » Extension Methods without 3.5 Framework — Sat, 17 Nov 2007 01:16:30 GMT

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re: Extension Methods without 3.5 Framework

Adrian Anttila — Sat, 17 Nov 2007 01:50:37 GMT

Could you provide a sample implementation? I've tried to implement this in C#, and I'm getting "Type expected" compiler errors because of the use of the this keyword in following code:

public static bool IsEmailAddress(this string s)

You're also unclear if the ExtensionAttribute should decorate anything.

Is this all available in MSDN article you mention? If so, what's the URL?

re: Extension Methods without 3.5 Framework

Jared Parsons — Sat, 17 Nov 2007 02:00:26 GMT

Sorry for the confusion. Below is some sample code detailing how to get this to work in C#. For C# you don't need to decorate anything with the Extension attribute (C# has builtin syntax for extension methods).

using System;

using System.Collections.Generic;

using System.Text;

namespace System.Runtime.CompilerServices

{

class ExtensionAttribute : Attribute

{

}

namespace ConsoleApplication168

{

public static class ExtensionHolder

{

public static bool IsEmailAddress(this string s)

{

return false;

}

class Program

{

static void Main(string[] args)

{

}

re: Extension Methods without 3.5 Framework

Adrian Anttila — Sat, 17 Nov 2007 02:29:20 GMT

Here's my implementation, which still gets the "Type expected" compiler error in Visual Studio 2005:

using System;

using System.Runtime.CompilerServices;

using System.Text.RegularExpressions;

namespace System.Runtime.CompilerServices

{

public class ExtensionAttribute : Attribute

{

}

namespace ConsoleApplication1

{

public static class StringExtensions

{

public static bool IsEmailAddress(this string s)

{

Regex regex = new Regex(@"^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$");

return regex.IsMatch(s);

}

public class Program

{

public static void Main(string[] args)

{

string email = "aanttila@vertigo.com";

if (email.IsEmailAddress())

{

Console.Write("Valid");

}

else

{

Console.Write("Invalid");

}

Console.WriteLine();

Console.Write("Press <enter> to exit...");

Console.ReadLine();

}

Are you targeting the 2.0 runtime from VS2008? I wonder if the compiler in VS2005 won't support the new 3.0 language features even if they are valid for 2.0.

re: Extension Methods without 3.5 Framework

Adrian Anttila — Sat, 17 Nov 2007 02:29:20 GMT

Here's my implementation, which still gets the "Type expected" compiler error in Visual Studio 2005:

using System;

using System.Runtime.CompilerServices;

using System.Text.RegularExpressions;

namespace System.Runtime.CompilerServices

{

public class ExtensionAttribute : Attribute

{

}

namespace ConsoleApplication1

{

public static class StringExtensions

{

public static bool IsEmailAddress(this string s)

{

Regex regex = new Regex(@"^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$");

return regex.IsMatch(s);

}

public class Program

{

public static void Main(string[] args)

{

string email = "aanttila@vertigo.com";

if (email.IsEmailAddress())

{

Console.Write("Valid");

}

else

{

Console.Write("Invalid");

}

Console.WriteLine();

Console.Write("Press <enter> to exit...");

Console.ReadLine();

}

Are you targeting the 2.0 runtime from VS2008? I wonder if the compiler in VS2005 won't support the new 3.0 language features even if they are valid for 2.0.

re: Extension Methods without 3.5 Framework

Tony — Sat, 17 Nov 2007 02:30:46 GMT

Actually, the C# version you wrote still will not compile because of that same error message.

re: Extension Methods without 3.5 Framework

Jared Parsons — Sat, 17 Nov 2007 02:36:16 GMT

This trick will only work with VS2008.

在 .NET Framework x (x

Adrian H. — Sat, 17 Nov 2007 17:19:09 GMT

扩展方法本质上只是一个编译器级别的语法糖, 但不引用.NET Framework 3.5的程序集却无法发布程序到2.0/3.0版本的运行环境中, 因为它将使那些方法(扩展方法)带上ExtensionAttribute属性, 而就是ExtensionAttribute这个类却存在于.NET Framework 3.5的程序集中. 其实只要使用一个小技巧即可以保证带有扩展方法的程序在Target到.NET Framework 2.0/3.0时通过编译...

re: Extension Methods without 3.5 Framework

alan — Tue, 20 Nov 2007 00:05:54 GMT

I just installed framework 3.5 so i could play with linq but can not seem to get extension methords working in VS2005.

MS you are a joke with you 3/3.5 framework and many developers think that V3.0 has linlq

Syntactic Sugar, Compiler Candy, and Other Sweets

James Kovacs — Tue, 15 Jan 2008 21:55:30 GMT

A great new feature of Visual Studio 2008 is multi-targeting, which allows VS 2008 to compile for .NET