Update: Visual Studio has this functionality baked in!
Edit -> Paste Special
The XML Schema Definition tool is packaged into the Windows SDK. This means I've had this tool on my machine for practically forever and have been doing things the hard way for a long time.
Your path to xsd.exe will look something like this depending on which version of the Windows SDK you have installed.
C:\Program Files (x86)\Microsoft SDKs\Windows\<version>\Bin\NETFX 4.0 Tools\xsd.exe
It's a two step process to convert an XML file to a corresponding set of C# classes: create an XSD from your XML and then create your C# classes from that XSD...
XML to XSD
The following will output <filename>.xsd
XSD to C# Classes
The following will output your csharp classes to a single file <filename>.cs - Note the '/l:cs' switch can be changed to '/l:vb' to output VB instead of C#
xsd.exe /c /l:cs file.xsd
And that's it! You should now have an auto-generated C# model. By default this file will be placed into the same directory as the xsd executable. You can also specify the **'-out:<directoryName>'**in order to change the location that your files get saved.