I have two fields I would like to merge into a formula field if field2 is not empty, otherwise put field 1 only in the formula field.

Here is what I have tried so far without success:

If(${Contacts.field2}!='',${Contacts.field1},${Contacts.field1}' &'${Contacts.field2})

If(isBlank(${Contacts.field2}),${Contacts.field1},${Contacts.field1}' &'${Contacts.field2})

If(isnull(${Contacts.field2}),${Contacts.field1},${Contacts.field1}' &'${Contacts.field2})

Any suggestions.