How do I get Linq to ignore any parameters that are empty? So Lastname, Firstname, etc? If I have data in all parameters it works fine.

refinedresult = From x In theresult _
                    Where x.<thelastname>.Value.TestPhoneElement(LastName) Or _
                    x.<thefirstname>.Value.TestPhoneElement(FirstName) Or _
                    x.<id>.Value.TestPhoneElement(Id) Or _
                    x.<number>.Value.TestPhoneElement(Telephone) Or _
                    x.<location>.Value.TestPhoneElement(Location) Or _
                    x.<building>.Value.TestPhoneElement(building) Or _
                    x.<department>.Value.TestPhoneElement(Department) _
                    Select x


Public Function TestPhoneElement(ByVal parent As String, ByVal value2compare As String) As Boolean
'find out if a value is null, if not then compare the passed value to see if it starts with
Dim ret As Boolean = False

If String.IsNullOrEmpty(parent) Then
    Return False
End If
If String.IsNullOrEmpty(value2compare) Then
    Return ret
Else
    ret = parent.ToLower.StartsWith(value2compare.ToLower.Trim)
End If

Return ret
End Function