/// <summary>
/// Returns a new change record that represents the total of this change
/// and the previous change.
/// </summary>
/// <param name="previousChange"></param>
/// <returns></returns>
public ChangeRecord Compound(ChangeRecord previousChange)
{
// assume the propertyDiffs array in both objects is aligned
var resultDiffs = new PropertyDiff[_propertyDiffs.Length];
for (var i = 0; i < _propertyDiffs.Length; i++)
{
resultDiffs[i] = _propertyDiffs[i].Compound(previousChange.PropertyDiffs[i]);
}
// return a new change record that represents the accumulation of both changes
// the resultant ChangeType depends on whether this change Supercedes previousChange, or vice versa
return new ChangeRecord(_entity, Supercedes(previousChange) ? _changeType : previousChange._changeType, resultDiffs);
}
/// <summary>
/// Returns a new change record that represents the total of this change
/// and the previous change.
/// </summary>
/// <param name="previousChange"></param>
/// <returns></returns>
public ChangeRecord Compound(ChangeRecord previousChange)
{
// assume the propertyDiffs array in both objects is aligned
var resultDiffs = new PropertyDiff[_propertyDiffs.Length];
for (var i = 0; i < _propertyDiffs.Length; i++)
{
resultDiffs[i] = _propertyDiffs[i].Compound(previousChange.PropertyDiffs[i]);
}
// return a new change record that represents the accumulation of both changes
// the resultant ChangeType depends on whether this change Supercedes previousChange, or vice versa
return(new ChangeRecord(_entity, Supercedes(previousChange) ? _changeType : previousChange._changeType, resultDiffs));
}
/// <summary>
/// Records that the specified change occured to the specified entity.
/// </summary>
/// <param name="entity"></param>
/// <param name="changeType"></param>
/// <param name="propertyDiffs"></param>
internal void RecordChange(Entity entity, EntityChangeType changeType, PropertyDiff[] propertyDiffs)
{
var thisChange = new ChangeRecord(entity, changeType, propertyDiffs);
// check if this entity was already recorded in the list
// note that reference equality is used because we do not know how the Equals method of the entity may be implemented
// for example, it may define equality based on a property whose value has changed, which would break this logic
var prevRecordIndex = _changeRecords.FindIndex(r => ReferenceEquals(r.Entity, entity));
if (prevRecordIndex > -1)
{
// this entity was already marked as changed
var previousChange = _changeRecords[prevRecordIndex];
// compound the previous change record with this one
_changeRecords[prevRecordIndex] = thisChange.Compound(previousChange);
}
else
{
// record this change in the change set
_changeRecords.Add(thisChange);
}
}
/// <summary>
/// Records that the specified change occured to the specified entity.
/// </summary>
/// <param name="entity"></param>
/// <param name="changeType"></param>
/// <param name="propertyDiffs"></param>
internal void RecordChange(Entity entity, EntityChangeType changeType, PropertyDiff[] propertyDiffs)
{
var thisChange = new ChangeRecord(entity, changeType, propertyDiffs);
// check if this entity was already recorded in the list
// note that reference equality is used because we do not know how the Equals method of the entity may be implemented
// for example, it may define equality based on a property whose value has changed, which would break this logic
var prevRecordIndex = _changeRecords.FindIndex(r => ReferenceEquals(r.Entity, entity));
if (prevRecordIndex > -1)
{
// this entity was already marked as changed
var previousChange = _changeRecords[prevRecordIndex];
// compound the previous change record with this one
_changeRecords[prevRecordIndex] = thisChange.Compound(previousChange);
}
else
{
// record this change in the change set
_changeRecords.Add(thisChange);
}
}
/// <summary>
/// Checks whether this change supercedes the specified other change. This change supercedes other iff
/// the <see cref="ChangeType"/> of this change is greater than the <see cref="ChangeType"/> of the other.
/// </summary>
/// <remarks>
/// The <see cref="EntityChangeType.Create"/> value supercedes <see cref="EntityChangeType.Update"/>, and
/// <see cref="EntityChangeType.Delete"/> supercedes both. In other words, a Create followed by an update
/// is fundamentally a Create, and a Create or Update followed by a Delete is fundamentally a Delete.
/// </remarks>
/// <param name="other"></param>
/// <returns></returns>
private bool Supercedes(ChangeRecord other)
{
return _changeType > other.ChangeType;
}
/// <summary>
/// Checks whether this change supercedes the specified other change. This change supercedes other iff
/// the <see cref="ChangeType"/> of this change is greater than the <see cref="ChangeType"/> of the other.
/// </summary>
/// <remarks>
/// The <see cref="EntityChangeType.Create"/> value supercedes <see cref="EntityChangeType.Update"/>, and
/// <see cref="EntityChangeType.Delete"/> supercedes both. In other words, a Create followed by an update
/// is fundamentally a Create, and a Create or Update followed by a Delete is fundamentally a Delete.
/// </remarks>
/// <param name="other"></param>
/// <returns></returns>
private bool Supercedes(ChangeRecord other)
{
return(_changeType > other.ChangeType);
}
