/// <summary>
/// Gets the value of the property on the object, instantiating it with a default
/// value if it is currently null.
/// </summary>
private object getValue(object model, PropertyInfo containerProperty)
{
var value = containerProperty.GetValue(model, null);
if (value == null)
{
value = HistoryHelpers.Instantiate(containerProperty.PropertyType);
containerProperty.SetValue(model, value, null);
}
return(value);
}
/// <summary>
/// Retrieve the values that a single property has gone through, most recent
/// first (descending date order).
/// </summary>
public virtual IEnumerable<IChange<TValue, TPrincipal>> ChangesTo<TModel, TValue>(TModel model, Expression<Func<TModel, TValue>> property)
{
string typeName = typeof(TModel).Name;
string propertyName = property.GetPropertyName();
string propertyPrefix = propertyName + ".";
string reference = historyContext.GetReferenceForObject(model);
var propertyFunc = property.Compile();
var objectChanges = changesTo(model)
.SelectMany(o => o.PropertyChanges)
.Where(p => p.PropertyName == propertyName || p.PropertyName.StartsWith(propertyPrefix))
.AsEnumerable()
.GroupBy(p => p.ObjectChange)
.Select(g => new FilteredObjectChange<TPrincipal>(g.Key, g));
// If the propert expression refers to a complex type then we will not have any changes
// directly to that property. Instead we will see changes to sub-properties.
// We retrieve the history differently for complex types, so here we distinguish which
// case we are in by looking at the first change.
var sample = objectChanges.SelectMany(o => o.PropertyChanges).FirstOrDefault();
if (sample != null && sample.PropertyName.StartsWith(propertyPrefix))
{
// Construct a "seed" instance of the complex type, and then apply changes to it in order
// to reconstruct the intermediate states.
return applyChangesTo(HistoryHelpers.Instantiate<TValue>(), objectChanges, propertyName)
.OrderByDescending(c => c.Timestamp);
}
else
{
// Just directly bind the simple property values
return objectChanges
.OrderByDescending(o => o.ChangeSet.Timestamp)
.SelectMany(o => o.PropertyChanges)
.Select(p => Change.FromObjectChange(binder.Bind<TValue>(p.Value), p.ObjectChange));
}
}
