Need to validate user input (domain user,group) and fetch detail - powershell

Question

When I supply a string and need to extract the domain user object (name, surname, manager name) I get the desired detail through following code.
$groupdetail : gc d:\domainobject.txt
$output = Get-ADUser $GroupDetail
$output | Select Name, GivenName,SurName, #{label="Manager";expression={(Get-ADUser $_.Manager -Properties DisplayName).Displayname}}
Next thing is validate of the input if it is a domain group then extract the group member names then get the user object information again as above. The problem is I am unable to validate if the string is a group.
$groupname = Get-content D:\domainobject.txt
foreach ($group in $groupname){
$groupname = get-adgroup $group
$groupmember = Get-ADGroupMember $groupname | Format-Table Name, SamAccountName -AutoSize
foreach ($groupdetail in $groupmember){
$groupdoutput = get-aduser $groupdetail
$groupoutput | Select-Object Name, GivenName,SurName, #{label="Manager";expression={(Get-ADUser $_.Manager -Properties DisplayName).Displayname}}
}
Write-Host $groupoutput
}
Both condition should run in one code so if the input string is a domain user get the information and exit. Incase string is a domain group it will loop in get the group member name then extract the domain user information. One way I thought is to run this condition $groupname.objectclass -eq "group" or $groupname.objectclass -eq "name" so that I need to convert the input string to PowerShell object.
I tried a few things but that did not work. Please suggest what are the possible way I can achieve this.

Answer 1

You could always use a try-catch block
try{$group = get-adgroup $groupname}
catch{$user = get-aduser $groupname}
if($group)
{write-host "It's a group!"}
else
{Write-host "It's a user!"}
That will tell you if it's a group or a user. Just replace the write-host with your logic.

Answer 2

Usually when doing this sort of thing, I want one of two things:
In the first case, if I want the groups that a user is a member of directly regardless of nesting, then I specify:
Get-AdUser -Identity 'Alice' -Properties MemberOf
This will return the MemberOf property with the user, which is a string array that in each element includes the distinguished name of a group the user is a direct member of. Depending on exactly what you're doing, it may make sense to fetch all groups from AD at once to get the group details en masse, and then do a lookup for each MemberOf.
In the second case, I only care about effective group membership of user accounts. I will want Get-AdGroupMember to resolve the nested groups into the resulting set of users. In other words, if I run Get-AdGroupMember -Identity 'Foo', and the members are user Alice and group Bar, and user Bob is a member of group Bar, then I want the cmdlet to return Alice and Bob. I don't care that Bar is the reason that Bob is in Foo. To do that, I run:
Get-AdGroupMember -Identity 'Foo' -Recurse