NHibernate Criteria - How to filter on combination of properties

问题

I needed to filter a list of results using the combination of two properties. A plain SQL statement would look like this:

SELECT TOP 10 *
FROM Person
WHERE FirstName + ' ' + LastName LIKE '%' + @Term + '%'

The ICriteria in NHibernate that I ended up using was:

ICriteria criteria = Session.CreateCriteria(typeof(Person));
criteria.Add(Expression.Sql(
    "FirstName + ' ' + LastName LIKE ?",
    "%" + term + "%",
    NHibernateUtil.String));
criteria.SetMaxResults(10);

It works perfectly, but I'm not sure if it is the ideal solution since I'm still learning about NHibernate's Criteria API. What are the recommended alternatives?

Is there something besides Expression.Sql that would perform the same operation? I tried Expression.Like but couldn't figure out how to combine the first and last names.
Should I map a FullName property to the formula "FirstName + ' ' + LastName" in the mapping class?
Should I create a read only FullName property on the domain object then map it to a column?

回答1:

You can do one of the following:

If you always work with the full name, it's probably best to have a single property
Create a query-only property for that purpose (see http://ayende.com/Blog/archive/2009/06/10/nhibernate-ndash-query-only-properties.aspx)
Do the query in HQL, which is better suited for free-form queries (it will probably be almost the same as your SQL)
Use a proper entity-based Criteria:

Session.CreateCriteria<Person>()
       .Add(Restrictions.Like(
            Projections.SqlFunction("concat",
                                    NHibernateUtil.String,
                                    Projections.Property("FirstName"),
                                    Projections.Constant(" "),
                                    Projections.Property("LastName")),
            term,
            MatchMode.Anywhere))

回答2:

On the pure technical side i don't have an answer, but consider this: since you are only have a single input field for the user to enter the term, you don't know if he is going to enter 'foo bar' or 'bar foo'... so i would recommend this:

ICriteria criteria = Session.CreateCriteria(typeof(Person));
criteria.Add(Expression.Like("FirstName",term, MatchMode.Anywhere) || Expression.Like("LastName",term, MatchMode.Anywhere));
criteria.SetMaxResults(10);

来源：https://stackoverflow.com/questions/2936700/nhibernate-criteria-how-to-filter-on-combination-of-properties

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nhibernate

expression

icriteria