problem getting network user id - svc-webapps shows up instead

I have an aspx page that uses some code behind to populate a textbox with the network user id...

            System.Security.Principal.WindowsIdentity a = System.Security.Principal.WindowsIdentity.GetCurrent();

            BoxRecordCreatedBy.Text = a.Name.Split(new char[] { '\\' })[1];

...and in my web config have windows authentication turned on...

    <authentication mode="Windows" />

...but was getting 404 error until I added this to my web.config...

  <appSettings>     <add key="owin:AutomaticAppStartup" value="false"/>   </appSettings>

...so now the page loads and when I run the page in debug my userid populates the textbox as expected but after I publish the page and access it it populates the textbox with a service account...

svc-webapps

Windows authentication is enabled on the IIS server as well.

Could someone kindly show me what I'm doing wrong and how to correct it?

Thanks as tonne, Roscoe