Guid should be treated as such DbType.

Using NPoco with PostgreSQL (npgsql) the following was not possible:

    database.Fetch<Table>("select * from table where guidcol=@0", myGuid);

I got a NpgsqlException: "ERROR: 42883: operator does not exist: uuid = text"

This was because NPoco tried to execute the following SQL:

select * from table where guidcol=((E'a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11')::text)

This fixes it, and I don't see any unit tests failing, so I'm not sure why the original code was to treat Guid as DbType.String.