/// <summary>
/// Helper method to update the DefaultableValue if and only if the value has changed
/// </summary>
/// <param name="existingValue">
/// existing value of attribute (StringOrNone.NoneValue indicates attribute
/// currently does not exist)
/// </param>
/// <param name="newValue">
/// new value of attribute passed into setter (null indicates user did not select
/// anything on the drop-down and so no setting should take place, StringOrNone.NoneValue indicates user
/// selected '(None)' on the drop-down and so attribute should be removed if present)
/// </param>
/// <param name="defaultableValueToUpdate"></param>
internal static void UpdateDefaultableValueIfValuesDiffer(
StringOrNone existingValue, StringOrNone newValue,
DefaultableValue<StringOrNone> defaultableValueToUpdate)
{
if (null == newValue)
{
// user exited drop-down without selecting anything
return;
}
if (existingValue.Equals(newValue))
{
// no change in value - so just return
return;
}
else
{
// existingValue and valueToSet are different - so update the DefaultableValue
// if newValue is NoneValue then set valueToSet to null which will remove the attribute
// otherwise use newValue as is
var valueToSet = (StringOrNone.NoneValue.Equals(newValue) ? null : newValue);
var cmd =
new UpdateDefaultableValueCommand<StringOrNone>(defaultableValueToUpdate, valueToSet);
var cpc = PropertyWindowViewModelHelper.GetCommandProcessorContext();
CommandProcessor.InvokeSingleCommand(cpc, cmd);
}
}
protected override void PreParse()
{
ClearEFObject(_localName);
_localName = null;
base.PreParse();
}