Library helps supporting old .NET frameworks like .NET 2.0 and 3.5. This is a backport from .NET Core. Following classes are provided:

• System.Action
• System.Tuple
• System.Collections.Concurrent.ConcurrentDictionary

Action and Func is quite tricky to use in a multi target framework project because 2.0, 3.0 and 3.5 framework just provided subset of them.

• .NET Framework 2.0, 3.0 supports only Action<T>
• .NET Framework 3.5 supports Action, Func has up to 4 parameters.
• .NET Framework 4.0 supports Action, Func has up to 16 parameters.

To deal with this problem, this library provides missing classes in target framework.

PM> Install-Package NetLegacySupport.Action 

Func<int,int,int,int,long>f=(a,b,c,d)=>{return(long)a+b+c+d;};Console.WriteLine(f(1,2,3,4));// 10

Until .NET Framework 4, tuple was not supported. But it's an essential class that makes your code terse.

PM> Install-Package NetLegacySupport.Tuple 

Tuple<int,string>t=Tuple.Create(1,"One");Console.WriteLine(t);// (1, "One")

ConcurrentDictionary is quite useful dictionary with a thread-safe feature. If your project is targeted toward .NET 3.5 only, Task Parallel Library for .NET 3.5 can be an option.

PM> Install-Package NetLegacySupport.ConcurrentDictionary 

// New instance. (from http://www.dotnetperls.com/concurrentdictionary)varcon=newConcurrentDictionary<string,int>();con.TryAdd("cat",1);con.TryAdd("dog",2);// Try to update if value is 4 (this fails).con.TryUpdate("cat",200,4);// Try to update if value is 1 (this works).con.TryUpdate("cat",100,1);// Write new value.Console.WriteLine(con["cat"]);