In ASP.NET, what determines the value of HostingEnvironment.IsDevelopmentEnvironment?

Question

The MSDN documentation does not explain how, when or why this value is set to true.

Setting <configuration debug="false" /> in web.config does not set the property to false, nor does setting <deployment retail="true" /> in machine.config.

I'm running the test website from Visual Studio 2012 on IIS Express, I do not have IIS 'proper' installed.

Edit: After reviewing Oscar's answer and doing some more research, it seems that setting <deployment retail="true" /> should override, so I probably didn't set it in the right framework's machine.config when I asked this question.

Answer 1

The decompiled code of this property is as follows:

public static bool IsDevelopmentEnvironment
{
    get
    {
        return ((AppDomain.CurrentDomain.GetData(".devEnvironment") as bool?) == true);
    }
}

But I couldn't fin where this value is set.. :-(