.NET Framework 4 and CLR 4

One of the first things to notice after installing .NET Framework 4, is a new folder representing framework 4 (v4.0.20506) got added in Framework folder – Windows Folder\Microsoft .NET\Framework. Notice the version no in folder name 4.0.20506 – there are other folders representing older .NET Frameworks 3.5, 3.0, 2.0, 1.1 and 1.0 (each represented as sub folders).


The property of System.dll in version 4 folder confirms the version no as 4.0 (4.0.20506). This version no also shows up when you check the property of System assembly within Visual Studio.


.NET Framework 4.0 also comes with a brand new version of Common Language Runtime (CLR) – CLR 4. 3.5 SP1, 3.5, 3.0 and 2.0 versions of .NET Frameworks all used the same version of CLR – CLR 2. With .NET Framework 4.0 there is a new CLR – CLR 4.


Apart from performance and other improvements in .NET Framework like DLR (Dynamic Language Runtime) related stuff, Contract (Design by Contract – earlier available as separate download from Dev Labs) there has been improvements in .NET 4 BCL (Base Class Library) like

  • System.Numerics namespace
    • BigInteger data type
  • Tuple<T> data structure – used extensively in DLR and Dynamic languages IronPython, IronRuby
  • SortedSet<T> data structure
  • IO related improvements

I’ll discuss the BCL improvements in a separate blog post next time – Happy coding in VS 2010/.NET 4


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