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PO"Compatibility Pack" for backporting new .NET Framework features?
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copied!<p>For various reasons I often find it desirable to write code that is compatible with .NET framework 2.0 or 3.5 or compatible with the .NET Compact Framework, but it is a problem that there are numerous "small" features in new .NET frameworks that are not available in the older frameworks or Compact Framework.</p> <p>For example, I find extension methods are really useful, but the compiler depends on <code>System.Runtime.CompilerServices.ExtensionAttribute</code> for this. You can easily define this attribute yourself and then use extension methods in .NET Framework 2.0 (under C# 3.0+). Likewise, it isn't too hard to manually define little .NET 4 types like <code>Tuple<T1,T2></code> and <code>Lazy<T></code>. By the way, if you want to use LINQ in .NET 2.0, you can use <a href="http://www.albahari.com/nutshell/linqbridge.aspx" rel="noreferrer">LinqBridge</a>.</p> <p>Now suppose you make the <code>ExtensionAttribute</code> public so that other assemblies you write can use it. That's fine at first, but what if you then want to use a 3rd party library that also had the same idea? You add a reference to that library and now you've got a name collision. Oops.</p> <p>I have also noticed that some new libraries are only available for .NET 4.0 or 3.5 even though they only have minor dependencies on it that could be resolved using a compatibility pack or LinqBridge.</p> <p>It would sure be nice if there were "compatibility packs" for older .NET versions that defined these little features in a small DLL that you could justify including in projects of any size. Does such a thing exist?</p> <p><strong>Update</strong>: Judging by the silence, I guess there's no such thing. I might make such a OSS library myself if there is interest. So my new question is, what <em>smaller</em> features of .NET 4 (as opposed to monsters like WCF/WPF) would you miss if you were writing for .NET 2, .NET 3.5, .NETCF or Silverlight? I'll start the list off...</p> <ul> <li><code>ExtensionAttribute</code> (not in .NET 2)</li> <li><code>Func<...></code> and <code>Action<...></code> delegates (not in .NET 2)</li> <li>LINQ-to-objects (not in .NET 2)</li> <li><code>Tuple<...></code> (not in .NET 3.5)</li> <li><code>Lazy<T></code> and <code>Lazy<T,TMetadata></code> (not in .NET 3.5)</li> <li>Expression Trees (not in .NET 2; incomplete in .NET 3.5)</li> <li>Generics Variance (exists in .NET 2 but inaccessible from C# 3 and VB 9)</li> <li><code>Reflection.Emit</code> (missing from .NETCF; not really a small feature but I miss it very much)</li> </ul>

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