/// <summary>
/// Find the property on the target type that acts as the back-link in the relationship
/// </summary>
/// <returns></returns>
private static PropertyInfo FindBackLink(Resource target, Resource value, ResourceReferenceAttribute referenceAtt)
{
var propOnTarget = (from prop in ReferenceProperties(target.GetType(), false)
where IsInstanceOfReference(prop, value)
let backAtt = prop.GetCustomAttribute <ResourceReferenceAttribute>()
where backAtt.Name == referenceAtt.Name && // Compare name
backAtt.RelationType == referenceAtt.RelationType && // Compare relation type
backAtt.Role != referenceAtt.Role // Validate inverse role
select prop).FirstOrDefault();
return(propOnTarget);
}
/// <summary>
/// Find all resources references by the instance with the same reference information
/// </summary>
private static ISet <IResource> CurrentReferences(Resource instance, ResourceReferenceAttribute referenceAtt)
{
// Get all references of this resource with the same relation information
var currentReferences = (from property in ReferenceProperties(instance.GetType(), false)
let att = property.GetCustomAttribute <ResourceReferenceAttribute>()
where att.RelationType == referenceAtt.RelationType &&
att.Name == referenceAtt.Name &&
att.Role == referenceAtt.Role
select property.GetValue(instance)).SelectMany(ExtractAllFromProperty);
return(new HashSet <IResource>(currentReferences));
}
/// <summary>
/// Remove the reference to the resource on a target object
/// </summary>
private void ClearOnTarget(Resource target, Resource value, ResourceReferenceAttribute referenceAtt)
{
var prop = FindBackLink(target, value, referenceAtt);
if (prop == null)
{
return; // No back-link -> nothing to do
}
// Update property ONLY if it currently points to our resource
var propValue = prop.GetValue(target);
if (propValue == value)
{
prop.SetValue(target, null);
}
else
{
(propValue as IReferenceCollection)?.UnderlyingCollection.Remove(value);
}
}
/// <summary>
/// Update backlink if possible
/// </summary>
private static void SetOnTarget(Resource target, Resource value, ResourceReferenceAttribute referenceAtt)
{
var prop = FindBackLink(target, value, referenceAtt);
if (prop == null)
{
return; // No back-link -> nothing to do
}
// Update back-link property
if (prop.PropertyType.IsInstanceOfType(value))
{
prop.SetValue(target, value);
}
else
{
var collection = prop.GetValue(target) as IReferenceCollection;
if (collection != null && !collection.UnderlyingCollection.Contains(value))
{
collection.UnderlyingCollection.Add(value);
}
}
}
/// <summary>
/// Set <see cref="ResourceRelation.SourceId"/> and <see cref="ResourceRelation.TargetId"/> depending on the <see cref="ResourceReferenceRole"/>
/// of the reference property
/// </summary>
private static void UpdateRelationEntity(ResourceEntity resource, ResourceEntity referencedResource, ResourceRelation relEntity, ResourceReferenceAttribute att)
{
if (att.Role == ResourceReferenceRole.Source)
{
relEntity.Source = referencedResource;
relEntity.Target = resource;
relEntity.SourceName = att.Name;
}
else
{
relEntity.Source = resource;
relEntity.Target = referencedResource;
relEntity.TargetName = att.Name;
}
}
/// <summary>
/// Create a <see cref="ResourceRelation"/> entity for a property match
/// </summary>
private static ResourceRelation CreateRelationForProperty(ReferenceSaverContext context, IResourceRelationRepository relationRepo, ResourceReferenceAttribute att)
{
var relationType = att.RelationType;
var relEntity = relationRepo.Create((int)relationType);
context.CreatedRelations.Add(relEntity);
return(relEntity);
}