Merge two objects to produce third using AutoMapper

Question

I know it\'s AutoMapper and not AutoMerge(r), but...

I\'ve started using AutoMapper and have a need to Map A -> B, and to add some properties from C so that B become

Answer 1

There is a nice example of merging multiple sources into a destination using autoMapper, here in Owain Wraggs' EMC Consulting Blog.

EDIT: To guard against the old "dead-link" syndrome, the essence of the code in Owain's blog is below.

/// 

/// Helper class to assist in mapping multiple entities to one single
/// entity.
/// 
/// 
/// Code courtesy of Owain Wraggs' EMC Consulting Blog
/// Ref:
///     http://consultingblogs.emc.com/owainwragg/archive/2010/12/22/automapper-mapping-from-multiple-objects.aspx
/// 
public static class EntityMapper
{
    /// 

    /// Maps the specified sources to the specified destination type.
    /// 
    /// The type of the destination
    /// The sources.
    /// 
    /// 
    /// Retrieve the person, address and comment entities 
    /// and map them on to a person view model entity.
    /// 
    /// var personId = 23;
    /// var person = _personTasks.GetPerson(personId);
    /// var address = _personTasks.GetAddress(personId);
    /// var comment = _personTasks.GetComment(personId);
    /// 
    /// var personViewModel = EntityMapper.Map(person, address, comment);
    /// 
    public static T Map(params object[] sources) where T : class
    {
        // If there are no sources just return the destination object
        if (!sources.Any())
        {
            return default(T);
        }

        // Get the inital source and map it
        var initialSource = sources[0];
        var mappingResult = Map(initialSource);

        // Now map the remaining source objects
        if (sources.Count() > 1)
        {
            Map(mappingResult, sources.Skip(1).ToArray());
        }

        // return the destination object
        return mappingResult;
    }

    /// 

    /// Maps the specified sources to the specified destination.
    /// 
    /// The destination.
    /// The sources.
    private static void Map(object destination, params object[] sources)
    {
        // If there are no sources just return the destination object
        if (!sources.Any())
        {
            return;
        }

        // Get the destination type
        var destinationType = destination.GetType();

        // Itereate through all of the sources...
        foreach (var source in sources)
        {
            // ... get the source type and map the source to the destination
            var sourceType = source.GetType();
            Mapper.Map(source, destination, sourceType, destinationType);
        }
    }

    /// 

    /// Maps the specified source to the destination.
    /// 
    /// type of teh destination
    /// The source.
    /// 
    private static T Map(object source) where T : class
    {
        // Get thr source and destination types
        var destinationType = typeof(T);
        var sourceType = source.GetType();

        // Get the destination using AutoMapper's Map
        var mappingResult = Mapper.Map(source, sourceType, destinationType);

        // Return the destination
        return mappingResult as T;
    }
}

The resultant calling code is nice an succinct.

    public ActionResult Index()
    {

        // Retrieve the person, address and comment entities and
        // map them on to a person view model entity
        var personId = 23;

        var person = _personTasks.GetPerson(personId);
        var address = _personTasks.GetAddress(personId);
        var comment = _personTasks.GetComment(personId);

        var personViewModel = EntityMapper.Map(person, address, comment);

        return this.View(personViewModel);
    }