/// <summary>
/// Returns a new record containing the ad-hoc schema and values that describes what are
/// the changes detected AT the original record compared against the target one, or null
/// if no changes can be detected.
/// <para>
/// The new record returned contains its own ad-hoc schema, cloned from the entries of
/// the original one, as well as the affected values that as they appeared in the source
/// record.
/// </para>
/// </summary>
/// <param name="source">The source record.</param>
/// <param name="target">The target record.</param>
/// <returns>A new record, with its ad-hoc schema, containing the changes, or null if no
/// changes can be detected.</returns>
public static IRecord Changes(this IRecord source, IRecord target)
{
if (source == null)
{
throw new NullReferenceException("Source cannot be null.");
}
if (source.IsDisposed)
{
throw new ObjectDisposedException(source.ToString());
}
if (source.Schema == null)
{
throw new InvalidOperationException("Source '{0}' carries no schema.".FormatWith(source));
}
if (target == null)
{
throw new ArgumentNullException("target", "Target cannot be null.");
}
if (target.IsDisposed)
{
throw new ObjectDisposedException(target.ToString());
}
if (target.Schema == null)
{
throw new InvalidOperationException("Target '{0}' carries no schema.".FormatWith(target));
}
var values = new List <object>();
var entries = new List <ISchemaEntry>();
for (int i = 0; i < source.Count; i++)
{
var sourceEntry = source.Schema[i];
var targetEntry = target.Schema.FindEntry(sourceEntry.TableName, sourceEntry.ColumnName);
if (targetEntry == null)
{
targetEntry = target.Schema.FindEntry(sourceEntry.ColumnName, raise: false);
}
if (targetEntry == null)
{
values.Add(source[i].TryClone());
entries.Add(sourceEntry.Clone());
}
else
{
var index = target.Schema.IndexOf(targetEntry);
var value = target[index];
var temp = source[i];
if (!temp.IsEquivalentTo(value))
{
values.Add(temp.TryClone());
entries.Add(sourceEntry.Clone());
}
}
}
if (entries.Count == 0)
{
return(null);
}
var schema = new Concrete.Schema(source.Schema.CaseSensitiveNames);
foreach (var entry in entries)
{
schema.Add(entry);
}
entries.Clear();
var record = new Concrete.Record(schema);
for (int i = 0; i < values.Count; i++)
{
record[i] = values[i];
}
values.Clear();
return(record);
}
/// <summary>
/// Returns a new instance that is a copy of the original one.
/// </summary>
/// <returns>A new instance.</returns>
public Schema Clone()
{
var cloned = new Schema(CaseSensitiveNames);
OnClone(cloned); return cloned;
}
