i need help with PowerShell

I need help with my script in logical comparison using a Csv: 
`SamAccountName`,`Othertelephone`,`employeeId`,`PreferredLanguage`
I have developed a script which update AD user details based on certain condition.

1. `EmployeeID` should be ABC and XYZ only, no other ID should be taken. and this field can be blank.
2. Sam Account cannot be blank
3. `Othertelephone` cannot be blank
4. `PreferredLanguage` should be EN|ES only.no other parameter should be taken and this field can be blank.

script will update user if above conditions are met.

I am stuck at point 1, it is not ignoring the blank field. if I leave it blank it executes the code block.

```
IF($_.employeeId -notmatch 'ABC|XYZ' or $_EmployeeId.trim() -eq "") 
{ write-output " Id is not proper" } 

```