Question

I have two classes. I want to map Class1 to a database table with linq to sql.

[Table(Name = "SomeTable")]
public class Class1
{
    public Class2 Class2
    {
        get; 
        set;
    }
}    

class Class2
{
    public string Name1
    {
        get;
        set;
    }

    public string Name2
    {
        get;
        set;
    }

    public string Name3
    {
        get;
        set;
    }
}

Database table has 3 columns corresponding to the Name-properties of Class2. In NHibernate f.ex., I would use a ‘component’-element in the xml-mapping, but how to do with linq to sql?

Answer 1

As far as I know, LINQ to SQL doesn’t allow this. But as almost always there are several workarounds for it.

The first one is to create a column-per-complex type property. See Complex Types in LINQ-to-SQL—Reloaded article for more details.

The second one is to associate class Class2 with a table and add a reference to it in Class1 (primary/foreign key).

And the last one is to store Class2 property of a type Class2 serialized. In the SomeTable it could be a column of type nvarchar(MAX) if you prefer JavaScriptSerializer or e.g. xml if you prefer serialization to XML.

Your complex type is pretty simple, so I show an example of how to do it by using JavaScriptSerializer. We should add a fake property of type Class2, and a private property of type string which will actually store the serialized value:

public partial class Class1
{
    // this is autogenerated property
    private string Class2Internal {...}

    // this is a fake property
    public Class2 Class2 {get; set;}

    partial void OnLoaded()
    {
        var serializer = new JavaScriptSerializer();
        this.Class2 = serializer.Deserialize<Class2>(this.Class2Internal);
    }

    partial void OnValidate(ChangeAction action)
    {
        var serializer = new JavaScriptSerializer();
        this.Class2Internal = serializer.Serialize(this.Class2);
    }
}

The OnLoaded is called after data is loaded by LINQ to SQL, and OnValidate is called before the code is saved – it’s the best place for serializing/deserializing (note, that serialization occurs only on saving, and deserialization on entity load).