Determine if SPPrincipal is SPUser, SPGroup or AD User

Question

Context

I have a List<SPPrincipal> that is a mix of SPGroup, SPUser and AD Users.

Problem

I'm trying to find out how to determine if an SPPrincipal I have is an SPUser, SPGroup or an AD user.

Attempted solutions

Ive tried something like:

foreach (var principal in listOfPrincipals
{
  if (principal is SPGroup) { /* do stuff */ }
}

But this does not appear to work.

Does anyone have any ideas about how to resolve this information ?

Update

After fiddling a bit I came to this solution that seems to work for SPGroup and SPUser

foreach (SPPrincipal subscriber in listOfSubscriberUsersAndGroups)
{
   var isGroup = subscriber is SPGroup;
   var isUser = subscriber is SPUser;
}

Here an SPGroup is found correctly, and SPUser is found correctly.

Update 2

The above actually works like it is supposed to. My mistake was that the SPPrincipal I was testing was actually a Domain-group, and not an SPGroup (red ears)

Answer 1

Are you sure that you provided correct code snippet? if it is true, the VS should throw this exception: 'Microsoft.SharePoint.SPPrincipal' is a 'type' but is used like a 'variable' and break build action. You should use principal variable instead of SPPrincipal class:

foreach (var principal in listOfPrincipals)
{
  if (principal is SPGroup) { //do stuff }
}

I tested this code:

SPPrincipal pr = SPContext.Current.Web.Groups[0];

if (pr is SPGroup)
{
    Console.WriteLine("Group");
}

And it works correctly.

Answer 2

You need to use the propriety Member

foreach (var principal in listOfPrincipals
{
  if (principal.Member is SPGroup) { /* do stuff */ }
  else if (principal.Member is SPUser) { /* do stuff */ }
}