Question

My Problem

“Source” object Properties of the same class that do not exist in the View, are overwritting the same properties in the “Target” object with nulls. How do I prevent this? In affect how do I ensure only populated(not null) properties are merged into the “Target” object. I have also tried this with Automapper and failed, but I would be happy with an Automapper solution as an alternative.

I do appreciate that this “Null Mapping” question has appeared before, but I fear my situation is more involved since there are nested objects. Well I tried the suggested options and I could not get them to work. So here I am.

Huge gratitude for any help.

I appreciate this is a complex problem, and really, really appreciate any help with this, particularly if someone can produce a code sample for me. I have pulling my hair out over this for a few days 🙁

What I have attempted

I have 2 objects, one is the original(“Target”), one(“Source”) is populated by a form ie a View.

The Original “Target” Object(myOrigDoc) looks like this:

The Form “Source” Object(myDoc) looks like this:

I then do the mapping:

            myOrigDoc.Introduction.InjectFrom<StrNotNull>(myDoc.Introduction);

using the following injector:

    public class StrNotNull: ConventionInjection
{
    bool blnNotNull = false;
    bool blnMatch = false;
    protected override bool Match(ConventionInfo c)
    {
        blnNotNull = false;
        blnMatch = false;

        //if ((c.SourceProp.Type == typeof(string)) && (c.SourceProp.Value != null))
        //    blnAssignable = true;

        if (c.SourceProp.Value != null)
            blnNotNull = true;

        if ((c.SourceProp.Name == c.TargetProp.Name) && (blnNotNull)) 
            blnMatch = true;

        return blnMatch;
    }
}

and I end up with:

The Form has no “DateOfBirth” field on it, therefore I suspect Model Binding is creating a null value for the “DataOfBirth” property, on the new “MyDoc” object, when I call:

        public ActionResult Index(Document myDoc)

Many thanks, Ed.

EDIT1: I believe this is a nested mapping problem due to the subclasses. Not sure how I sort this in ValueInjector.

EDIT2: Possible Automapper Solution from documentation for nested mappings, but I could not get it to work. I still get my nulls going across into the target.:

Mapper.CreateMap<XSD_Smart2.Document, XSD_Smart2.Document> 
().ForAllMembers(opt => opt.Condition(srs => !srs.IsSourceValueNull));

Mapper.CreateMap<XSD_Smart2.DocumentIntroduction, XSD_Smart2.DocumentIntroduction>  
().ForAllMembers(opt => opt.Condition(srs => !srs.IsSourceValueNull));

Mapper.CreateMap<XSD_Smart2.Client, XSD_Smart2.Client>().ForAllMembers(opt => 
opt.Condition(srs => !srs.IsSourceValueNull));

Answer 1

Update for ValueInjecter 3

public class IgnoreNulls : LoopInjection
{
    protected override void SetValue(object source, object target, PropertyInfo sp, PropertyInfo tp)
    {
        var val = sp.GetValue(source);
        if (val != null)
        {
            tp.SetValue(target, val);
        }
    }
}

---

previous version

create a custom injection that will have this behaviour:

    public class IgnoreNulls : ConventionInjection
    {
        protected override bool Match(ConventionInfo c)
        {
            return c.SourceProp.Name == c.TargetProp.Name
                  && c.SourceProp.Value != null;
        }
    }

and use it:

    target.InjectFrom<IgnoreNulls>(source);