System.IO.Compression.FileSystem not found with VS 2010 Express 4.5.50938 <p>I have VS 2010 Express 4.5.50938, but when I go to add a reference there is no System.IO.Compression.FileSystem under .NET tab, but I found a 4.0 version under the Recent Tab. When program runs I receive:</p> <pre><code>Warning 1 Reference to type 'System.IO.Compression.CompressionLevel' claims it is defined in 'c:\Program Files\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.0\Profile\Client\System.dll', but it could not be found c:\Windows\Microsoft.NET\assembly\GAC_MSIL\System.IO.Compression.FileSystem\v4.0_4.0.0.0__b77a5c561934e089\System.IO.Compression.FileSystem.dll Zip_Copy_To_Public </code></pre> <p>Do I copy the dll into this directory? </p>