C#•2y ago

❔ IQueryable implementation

I have a query that I want to order by location

.OrderBy(x => (x as ILocatable).DistanceTo(request.Longitude, request.Latitude))

.OrderBy(x => (x as ILocatable).DistanceTo(request.Longitude, request.Latitude))

however I get an error

System.InvalidOperationException: The LINQ expression 'DbSet<City>()
    .OrderBy(c => ((c as ILocatable)).DistanceTo(
        longitude: __request_Longitude_0, 
        latitude: __request_Latitude_1))' could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'. See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.

System.InvalidOperationException: The LINQ expression 'DbSet<City>()
    .OrderBy(c => ((c as ILocatable)).DistanceTo(
        longitude: __request_Longitude_0, 
        latitude: __request_Latitude_1))' could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'. See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.

which is expected, the function:

 public double DistanceTo(double longitude, double latitude)
    {
        const double R = 6371; // Earth radius in kilometers

        var dLat = (latitude - Latitude) * Math.PI / 180;
        var dLon = (longitude - Longitude) * Math.PI / 180;
        var lat1 = Latitude * Math.PI / 180;
        var lat2 = latitude * Math.PI / 180;

        var a = Math.Sin(dLat / 2) * Math.Sin(dLat / 2) +
                Math.Sin(dLon / 2) * Math.Sin(dLon / 2) * Math.Cos(lat1) * Math.Cos(lat2);
        var c = 2 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1 - a));

        return R * c;
    }

 public double DistanceTo(double longitude, double latitude)
    {
        const double R = 6371; // Earth radius in kilometers

        var dLat = (latitude - Latitude) * Math.PI / 180;
        var dLon = (longitude - Longitude) * Math.PI / 180;
        var lat1 = Latitude * Math.PI / 180;
        var lat2 = latitude * Math.PI / 180;

        var a = Math.Sin(dLat / 2) * Math.Sin(dLat / 2) +
                Math.Sin(dLon / 2) * Math.Sin(dLon / 2) * Math.Cos(lat1) * Math.Cos(lat2);
        var c = 2 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1 - a));

        return R * c;
    }

is it feasible to implement the translation or should I just do AsEnumerable?

4 Replies

TimberStalker•2y ago

I think this is an issue with EntityFramework not Linq

Angius•2y ago

Well, yes

TimberStalker•2y ago

If you want you can look up c# expression trees, which is the feature used for translating the query

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ IQueryable implementation