CurrentUser is null on Sharepoint 2010 application page

Question

I have application page, hosted on Sharepoint server (for ex. http://myportal/mysite/_layouts/application/default.aspx), which has code like this:

protected void Page_PreLoad(object sender, EventArgs e)
{           
    var userEmail = SPContext.Current.Web.CurrentUser.Email;
}

If user tries to get this page directly by URL after browser starts, exception appears, because CurrentUser is null. But if user firstly navigates to web site (http://myportal/mysite) and then to application page, CurrentUser is not null. So, how can I get CurrentUser object if it is not initialized in SPContext?

Answer 1

Getting the current user from an elevated SPWeb inside a RunWithElevatedPrivileges code. Try this code.

SPWeb site = SPContext.Current.Web;
SPSecurity.RunWithElevatedPrivileges(delegate()
{
    using (SPSite ElevatedsiteColl = new SPSite(site.Url))
   {
       using (SPWeb ElevatedSite = ElevatedsiteColl.OpenWeb())
       {
            SPUser currUser = site.CurrentUser; //not the ElevatedSite.CurrentUser
       }
   }
});

Answer 2

Well... better late than never. I ran into this same problem today. The previous comment does not address the original poster's expressed problem. The problems comes when you publish .ASPX pages in the _Layouts folder, and then, when using Forms or Claims auth, make that custom page your first hit in a session (with no previously remembered login). SharePoint authentication isn't fired by default (even if you inherit from the LayoutsPageBase class). If you navigate to some other SharePoint page (such as _Layouts/15/Settings.aspx) and then come back, then the CurrentUser is filled in. I had to use Reflector to get a better clue of what was going on, and how to fix it. The short answer is, once you realize that the CurrentUser == null, you need to add this line of code:

Microsoft.SharePoint.Utilities.SPUtility.HandleAccessDenied(new UnauthorizedAccessException());

In my case, this code generates a challenge/response to the browser, which I used to log in, and immediately following this line of code, the CurrentUser object is filled in correctly. Here is what my entire function ended up looking like:

public static bool isAdminAuthorized()
{
    Microsoft.SharePoint.SPContext oContext ;
    Microsoft.SharePoint.SPWeb oWeb ;
    Microsoft.SharePoint.SPUser oUser ;
    try
    {
        oContext = Microsoft.SharePoint.SPContext.Current;
    }
    catch { throw new Exception("Can't obtain Sharepoint Context!"); }
    try
    {
        oWeb = oContext.Web;
    }
    catch { throw new Exception("Can't obtain Sharepoint web!"); }
    try
    {
        oUser = oWeb.CurrentUser;
    }
    catch { throw new Exception("Can't obtain Sharepoint current user!"); }
    if (oUser == null)
    {
        Microsoft.SharePoint.Utilities.SPUtility.HandleAccessDenied(new UnauthorizedAccessException());
        oUser = oWeb.CurrentUser;
    }
    foreach (Microsoft.SharePoint.SPGroup oGroup in oUser.Groups)
    {
        if (oGroup.Name.ToUpper().Contains("OWNER"))
        {
            return true;
        }
    }
    return false;
}