Configure WPF client to run 64bit

Perhaps you are confusing the Visual Studio C# Platform with the Platform target?

Each Visual Studio C# project can be built to one of several platforms. This allows you to use the same project to build to several hardware platforms like 32 and 64 bit Intel/AMD CPU or even a different CPU like Itanium.

However, when you create a new project it will by default only contain a single platform, and in your case you also want to build to only a single platform, i.e. x64. For new projects the platforms used by Visual Studio are these:

• A library project (including a test project) will have the Any CPU platform.
• An executable project (including a WPF project) will have the x86 platform.

What is slightly confusing is that these platforms are just names hinting at what is actually built. You control what is emitted by the compiler in the Build tab of the project settings. Here you can set the Platform target to values like Any CPU, x86 or x64.

You will have to set the Platform target to x64 in your WPF project.

To fully configure your platforms you will have to use the Configuration Manager which is on the menu Build -> Configuration Manager.