I have added a new project to my solution. I have set the target platform of all my other projects in the solution to x64. For the new project, when I open the Configuration Manager there is no option for x64 in the drop down while my other similar projects have this option. The options I have are Any CPU, <New...> and <Edit...>. How can I set the platform to x64?
Choose new and then select x64 from the available platforms. There is also an option to copy settings from an existing type - e.g. AnyCPU and an option to apply to all projects. Normally copying settings from AnyCPU and applying to all projects is what you want then you can customize the x64 version as you require.