/// <summary>
/// Selects the items that match the specified filter.
/// </summary>
public IEnumerable <T> Select(TableFilter filter, bool indexRequired = false)
{
foreach (object item in SelectItems(filter, indexRequired))
{
yield return((T)item);
}
}
/// <summary>
/// Selects the first item that match the specified filter, or null.
/// </summary>
public T SelectFirst(TableFilter filter, bool indexRequired = false)
{
foreach (object item in SelectItems(filter, indexRequired))
{
return((T)item);
}
return(default);
/// <summary>
/// Selects the items that match the specified filter.
/// </summary>
public IEnumerable SelectItems(TableFilter filter, bool indexRequired = false)
{
if (filter == null)
{
throw new ArgumentNullException(nameof(filter));
}
// find the property used by the filter
PropertyDescriptor filterProp = TypeDescriptor.GetProperties(ItemType)[filter.ColumnName];
if (filterProp == null)
{
throw new ArgumentException("The filter property not found.");
}
// get the matched items
if (TryGetIndex(filter.ColumnName, out TableIndex index))
{
int indexKey = filter.Argument == null ? 0 : (int)filter.Argument;
foreach (object item in index.SelectItems(indexKey))
{
yield return(item);
}
}
else if (indexRequired)
{
throw new ScadaException("Index not found.");
}
else
{
object filterArg = filter.Argument;
foreach (T item in Items.Values)
{
object propVal = filterProp.GetValue(item);
if (Equals(propVal, filterArg))
{
yield return(item);
}
}
}
}