AutoMapper: Set all properties of destination object to default if source object is null for specified types

Question

Is it possible to configure AutoMapper to set all properties to default value in case if the source object is null for specified classes? I know that I should use Mapper.AllowNullDestinationValues = false; to do what I want for all classes in application. Here the sampled code that I use for tests, but it doesn't work

public class A
{
    static A()
    {
        Mapper.Initialize(
            config =>
                {
                    config.ForSourceType<B>().AllowNullDestinationValues = false;
                    config.CreateMap<B, A>()
                        .ForMember(member => member.Name, opt => opt.Ignore());
                });
        //Mapper.AllowNullDestinationValues = false;

        Mapper.AssertConfigurationIsValid();
    }

    public void Init(B b)
    {
        Mapper.DynamicMap(b, this);
    }

    public int? Foo { get; set; }
    public double? Foo1 { get; set; }
    public bool Foo2 { get; set; }
    public string Name { get; set; }
}

public class B
{
    public string Name { get; set; }
    public int? Foo { get; set; }
    public double? Foo1 { get; set; }
    public bool Foo2 { get; set; }
}

Using of this code:

var b = new B() {Foo = 1, Foo1 = 3.3, Foo2 = true, Name = "123"};
var a = new A {Name = "aName"};
a.Init(b);      // All ok: Name=aName, Foo=1, Foo1=3,3, Foo2=True
a.Init(null);   // Should be Name=aName, Foo=null, Foo1=null, Foo2=False, 
                // but a has the same values as on a previous line

Did you see this question?: http://stackoverflow.com/questions/3407838/automapper-create-instance-of-destination-type-if-source-null — Davin Tryon, Sep 20 '12 at 13:00
Yes, I saw that topic, but i think that `Mapper.AllowNullDestinationValues = false;` and `Mapper.Configuration.AllowNullDestinationValues = false;` the same — dmolokanov, Sep 20 '12 at 14:04
Could you explain, what this flag means, please? I can't find official documentation about it. — dmolokanov, Sep 20 '12 at 14:10

score 1 · Answer 1 · answered Sep 21 '12 at 02:52

It must be related to "a" being already mapped.

var a = new A {Name = "aName"};
a.Init(b);
a.Init(null);

All mappings are cached, so if you'll attempt to re-map same instance the automapper would just keep the original result.

In order to test it, try:

        var c = new A {Name = "x"};
        c.Init(null);

Here is a link to similar question.

score 0 · Answer 2 · answered Sep 20 '12 at 13:05

Looks like it will replace with null if you set Mapper.Configuration.AllowNullDestinationValues = false:

public class A
    {
        static A()
        {
            Mapper.Initialize(
                config =>
                {
                    config.ForSourceType<B>().AllowNullDestinationValues = false;
                    config.CreateMap<B, A>()
                        .ForMember(member => member.Name, opt => opt.Ignore());
                });
            Mapper.Configuration.AllowNullDestinationValues = false;

            Mapper.AssertConfigurationIsValid();
        }

        public void Init(B b)
        {
            Mapper.DynamicMap(b, this);
        }

        public int? Foo { get; set; }
        public double? Foo1 { get; set; }
        public bool Foo2 { get; set; }
        public string Name { get; set; }
    }

AutoMapper: Set all properties of destination object to default if source object is null for specified types

2 Answers2