My English teacher told me that "dashes and commas are interchangeable".
For instance, "My friend, Alex, ran to the store." and, "My friend–Alex–ran to the store." are both grammatically correct sentences and have the same meaning.
However, is, "My friend–Alex, ran to the store." a correct sentence? Or can the sentence only have one or the other when a dependent clause is inserted into an independent clause like that?