Check CSV for object not matching?

Probably a really elementary question but preliminary searches didn't return much. I'm writing a script that takes ID's ($CSC) from a .csv and populates the relevant information based off that ID.

Foreach ($row in $roster) {
    If ($CSC -eq $row.CSC) { 
        $Department = $row.Department
        $Division = $row.Division
        $Street = $row.Street
        $City = $row.City
        $State = $row.State
        $Zipcode = $row.Zipcode
        $OfficePhone = $row.Phone
        $Country = $row.Country
    } Else {    }
}

That's working fine but how would I check if a user input ID didn't match an ID in the list?

Making the else or making an elseif ($CSC -ne $row) obviously returns a value for every line except the matching one. I'm guessing I should use a nested if statement but being self taught I wasn't sure what the best way to do this is. Thanks.