This handler called when feature is being rebuilt (either when regenerate is invoked or when the parent elements have been changed).

Use MacroFeatureRebuildResult class to generate the required output.

Feature can generate the following output

using CodeStack.SwEx.MacroFeature;
using CodeStack.SwEx.MacroFeature.Base;
using CodeStack.SwEx.MacroFeature.Data;
using SolidWorks.Interop.sldworks;

namespace CodeStack.SwEx
{
    //returns successful regeneration without bodies
    public class RegenerationNoResultsMacroFeature : MacroFeatureEx
    {
        protected override MacroFeatureRebuildResult OnRebuild(ISldWorks app, IModelDoc2 model, IFeature feature)
        {
            return MacroFeatureRebuildResult.FromStatus(true);
        }
    }

    // returns regeneration error
    public class RegenerationRebuildErrorMacroFeature : MacroFeatureEx
    {
        protected override MacroFeatureRebuildResult OnRebuild(ISldWorks app, IModelDoc2 model, IFeature feature)
        {
            return MacroFeatureRebuildResult.FromStatus(false, "Failed to regenerate this feature");
        }
    }

    //return body without automatically assigning ids
    public class RegenerationBodyMacroFeature : MacroFeatureEx
    {
        protected override MacroFeatureRebuildResult OnRebuild(ISldWorks app, IModelDoc2 model, IFeature feature)
        {
            //use extension methods of IModeler to create a box body
            IBody2 tempBody = app.IGetModeler().CreateBox(new Point(0, 0, 0), new Vector(1, 0, 0), 0.1, 0.1, 0.1);

            return MacroFeatureRebuildResult.FromBody(tempBody, feature.GetDefinition() as IMacroFeatureData, false); 
        }
    }

    //return pattern of bodies and automatically assign entity ids
    public class RegenerationArrayOfBodiesMacroFeature : MacroFeatureEx
    {
        protected override MacroFeatureRebuildResult OnRebuild(ISldWorks app, IModelDoc2 model, IFeature feature)
        {
            IBody2[] tempBodies = null; //TODO: create temp bodies
            return MacroFeatureRebuildResult.FromBodies(tempBodies, feature.GetDefinition() as IMacroFeatureData, true);
        }
    }
}

Use IModeler interface if feature needs to create new bodies. Only temp bodies can be returned from the regeneration method.

Use extension methods available in the IModelerExtension class.