/// <summary>
/// Build "order by" using the specified generic field name.
/// </summary>
/// <param name="sortField">official field name (not the column name)</param>
/// <param name="entity"></param>
/// <param name="descending">true for descending sort, false for ascending sort</param>
/// <returns>empty string if sortField not defined for this station entity.</returns>
public static string AddSortOrder(string sortField, StationEntity entity,
bool descending)
{
string orderBy = "";
StationField sf = entity.GetField(sortField);
if (sf != null)
{
orderBy += " order by " + sf.Location + " ";
if (descending) orderBy += "desc ";
}
return orderBy;
}
/// <summary>
/// Helper methods to build SQL queries.
/// Not used recently since using Entity Framework instead.
/// </summary>
/// <summary>
/// Build database SQL query clause for multiple criteria.
/// TODO could add a "joiner" operator to use between multiple clauses (OR, AND)
/// </summary>
/// <param name="prefix">operator to precede clause, e.g. "AND"</param>
/// <param name="crit">set of Criterion (in a Collection)</param>
/// <param name="entity"></param>
/// <returns></returns>
public static string BuildQueryClause(string prefix, ICollection<Criterion> crit, StationEntity entity)
{
string clause = "";
foreach (Criterion c in crit)
{
// ignore "TYPE" criteria when building query
if (c.FieldName == (Field.EntityType)) continue;
// if we have already added a clause, use "AND" to join the next clause
if (clause.Length > 0) prefix = "AND";
// get the implementation details for this field in this station
StationField sf = entity.GetField(c.FieldName);
// TODO should we just return an empty string instead?
// risk is returning too many results
// this could be configurable if we make this a separate instantiable class
if (sf == null) throw new StationUnsupportedCriterionException(
"Station doesn't support field " + c.FieldName);
string type = sf.Type;
// TODO for now, we assume types are generic types.
// when we want to extend with custom types, we will need another
// mechanism to handle building queries for custom types.
if (type == (Field.TextType))
clause += AddSqlTextClause(prefix, sf, c);
else if (type == (Field.NumberType))
clause += AddSqlNumberClause(prefix, sf, c);
else if (type == (Field.DateType))
clause += AddSqlDateClause(prefix, sf, c);
// TODO implement clause builders for other data types : BOOLEAN
else throw new Exception("Field type not yet implemented: " + type);
}
return clause;
}