Configure Webmatrix for Windows Users

I create asp .net page and i have use windows user to authenticate.

<authentication mode="Windows" />

I create simply page with one label and display information.

if (Page.User.Identity.IsAuthenticated)
{
        Label1.Text = "Authenticated = 'TRUE'<br/>";
        Label1.Text = Page.User.Identity.Name;
}
else
{
        Label1.Text = "Authenticated = 'FALSE'<br/>";
}

I often get Authenticated = 'FALSE'

How configure web.config and WebMatrix to take user from Windows?

Probably you published your web site without changing authentication on the corresponding virtual directory of IIS.

You should deactivate "Anonymous" authentication and activate "Windows" authentication. The existence of <authentication mode="Windows" /> line in web.config is not enough for IIS. Moreover "Windows" authentication must be installed of cause (see for example this for more information).

try

<appSettings>
  <add key="enableSimpleMembership" value="false" />
</appSettings>