The Web application at XXX could not be found when using SharePoint Console

When using SharePoint 2010 Server OM code  on a Windows 2008 64 bit server, you get below exception :

The Web application at http://servername:portnumber/sitename/ could not be found. Verify that you have typed the URL correctly. If the URL should be serving existing content, the system administrator may need to add a new request URL mapping to the intended application.

You are using a very simple code and the exception occurs at the very first line while opening new instance of an SPSite :

using (SPSite osite = new SPSite("http://blrs2r11-1c/"))
        {
            using (SPWeb oweb = osite.OpenWeb())
            {
               // Response.Write(oweb.Title);
                Label1.Text = oweb.Title;
            }
        }

The solution is in your visual studio, change the target platform to 64 bit.

Update: Or you may not have permission to run the code.