Mapping list of strings in nhibernate

Question

My entity has besides other properties Keyword property which is of type list of strings.

public virtual IList<string> Keywords { get; set; }

so I tried to map this property using conformist mapping by code approach simple as possible like this

Property(x => x.Keywords);

but I'm getting following exception

NHibernate.MappingException : Could not determine type for: System.Collections.Generic.IList`1[[System.String, mscorlib, Version=4.0.0.0,.....

How's Keywords represented in your database if you don't mind me asking ? — Dimitar Dimitrov
– Dimitar Dimitrov, Commented Sep 17, 2013 at 10:20
@AlessandroD'Andria My db model is fine thank you :) What do you mean exactly ? — panjo
– panjo, Commented Sep 17, 2013 at 10:29
Hehehe, as @DimitarDimitrov point, how you represents KeyWords in DB, eg: I have a table Document with a relation many to many with a table KeyWord. — Alessandro D'Andria
– Alessandro D'Andria, Commented Sep 17, 2013 at 10:32

Patko · Accepted Answer · 2013-09-17 10:52:38Z

1

You could map this to a private string field and then use string.Split in your Keywords getter to get a list.

public class MyClass {
    private string _keywords;

    public virtual IEnumerable<string> Keywords {
        get { return _keywords.Split(','); }
        set { _keywords = string.Join(value, ","); }
    }
}

I am not familiar with mapping by code that NH uses (I use FluentNH) but your mapping would probably be something like this:

Map("_keywords", map => {
    map.Access(Access.Field);
    // ...
});

edited Sep 17, 2013 at 10:52

answered Sep 17, 2013 at 10:37

Patko

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1 Comment

Alessandro D'Andria Over a year ago

It's right but use public virtual string DbKeyWords { get; set; } instead of _keyword or NHibernate cannot map.

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