getting windows username instead of logged in user name in asp .net web form 4.5

Web Config:

    <authentication mode="Forms">
      <forms loginUrl="/Public/Login.aspx" protection="All" timeout="30" name=".ASPXAUTH" path="/" requireSSL="false" slidingExpiration="true" defaultUrl="default.aspx" cookieless="UseDeviceProfile" enableCrossAppRedirects="false"/>
    </authentication>

Loggin Code:


    if (userLoginResults.UserLoginStatus == UserLoginStatus.Successful)
            {
                var email = UserName.Text.ToLower().Trim();

                if (userLoginResults.Contains(UserRoleNames.Admin))
                {
                    FormsAuthentication.RedirectFromLoginPage(email, RememberMe.Checked);
                    Session["isMemberLoggedIn"] = true;
                    Response.Redirect("~/AdminPanel/Default.aspx");
                }
}

//
 var email = User.Identity.Name;

I did login by admin@admin.com  but i am getting DESKTOP-OPT261T\\mobasshir. this is my windows username..
How can i solve this?

I am using windows 10. microsoft visual studio professional 2013


 Thanks all