The basic functionality (given type X import namespace Y) is built into Visual Studio since who-knows-when [1].
In my opinion if you are doing a lot of commercial .NET development then ReSharper isn't an optional extra. Rather, it's money well spent. You get more complete functionality: ReSharper 8 added the smarts to look for NuGet packages in your solution and reference the correct NuGet package. (This is ALT+ENTER and it basically gets the right type and dependency first time around.)
ReSharper 9 goes further and allows you to find types in any package on NuGet - JetBrains maintains their own index of NuGet packages for this purpose [2].
[1] http://stackoverflow.com/a/186920/242520
[2] https://www.jetbrains.com/resharper/whatsnew/whatsnew_9.html...