/// <summary>
/// Filters a sequence of <see cref="IGeoCode"/> items based on a specified <see cref="GeoCodeRange"/>.
/// Useful for database queries for better performance.
/// </summary>
public static IQueryable <T> WhereInGeoCodeRange <T>(
this IQueryable <T> query,
GeoCodeRange geoCodeRange)
where T : IGeoCode
{
if (query == null)
{
throw new ArgumentNullException(nameof(query));
}
if (geoCodeRange == null)
{
throw new ArgumentNullException(nameof(geoCodeRange));
}
// The logic for bounding coordinates is different depending on whether geoCodeRange includes the 180th meridian.
Expression <Func <IGeoCode, bool> > geoCodeRangePredicate = geoCodeRange.IncludesMeridian180()
? (Expression <Func <IGeoCode, bool> >)(x =>
(x.LatitudeGeoCode >= geoCodeRange.MinimumLatitude && x.LatitudeGeoCode <= geoCodeRange.MaximumLatitude) &&
(x.LongitudeGeoCode >= geoCodeRange.MinimumLongitude || x.LongitudeGeoCode <= geoCodeRange.MaximumLongitude)
)
: x =>
(x.LatitudeGeoCode >= geoCodeRange.MinimumLatitude && x.LatitudeGeoCode <= geoCodeRange.MaximumLatitude) &&
(x.LongitudeGeoCode >= geoCodeRange.MinimumLongitude && x.LongitudeGeoCode <= geoCodeRange.MaximumLongitude);
return(((IQueryable <IGeoCode>)query)
.Where(geoCodeRangePredicate)
.Cast <T>());
}
/// <summary>
/// Returns true if the <see cref="GeoCodeRange"/> spans the 180th meridian.
/// </summary>
public static bool IncludesMeridian180(this GeoCodeRange geoCodeRange)
{
if (geoCodeRange == null)
{
throw new ArgumentNullException(nameof(geoCodeRange));
}
return(geoCodeRange.MinimumLongitude > geoCodeRange.MaximumLongitude);
}