private void CheckMapping()
{
foreach (PropertyType slot in this.SchemaRoot.PropertyTypes)
if (slot.DataType == _dataType && slot.Mapping == _mapping)
throw new InvalidSchemaException(String.Concat(SR.Exceptions.Schema.Msg_MappingAlreadyExists, ": name=", this.Name, ", dataType", _dataType, ", mapping", _mapping));
}