Question

I have an ASP.NET MVC 3 .NET application under Visual web developer Express 2010.

By default it is build as ‘Any CPU’. When tested, Environment.Is64BitProcess always returns false (I have Windows 7 64 bit). I tried Stack Overflow question Change target CPU settings in Visual Studio 2010 Express for both x86 and x64, but it always results in an error, something along the lines of:

Cannot load type 'MyApp.UI.MvcApplication'.

and points to the global.asax file with only one line:

<%@ Application Codebehind="Global.asax.cs" Inherits="MyApp.UI.MvcApplication" Language="C#" %>

How could I fix it?

Answer 1

This all depends on what process is hosting your website.

• If you are using Cassini or IIS Express, it will always be a 32-bit application because those processes are always 32-bit.

• If you are using IIS, then it depends on what your AppPool is set to.

The CPU settings affect what it can run under, not what it should.

• Any CPU means that the assembly is capable of running as 64-bit or 32-bit.
• x86 means it can only run in a 32-bit process.
• x64 means it cano only run in a 64-bit process.

These settings are more typical when you have different assemblies for different platforms, say if they have very specific platform invoke for each. Or if you have a stand alone executable that you want to always run 32-bit, even on a 64-bit environment. Generally, for ASP.NET you want your assemblies to to be Any CPU and use IIS’s configuration to decide if you are going to use a 32-bit or 64-bit AppPool.

For IIS 7+, you would look under the Advanced Settings of the App Pool. Set Enabled 32-bit applications to True for 32-bit, or False for 64-bit.

If you website is running on IIS Express or Cassini, then you don’t have a choice.