New Post: Could not load file or assembly 'R.NET' or one of its dependencies. An attempt was made to load a program with an incorrect format.

Well now I am getting Dll was not found.

var envPath = Environment.GetEnvironmentVariable("PATH");
var rBinPath = @"C:\Program Files\R\R-2.15.2\bin\x64"; // path is correct
Environment.SetEnvironmentVariable("PATH", envPath + Path.PathSeparator + rBinPath);
using (REngine engine = REngine.CreateInstance("RDotNet"))

I go that working I had to change the path to i386