CODEWITHSUNDEEP
c#linqlambda
markzzz
markzzz

Reputation: 48045

What's wrong with this Lambda expression?

This is my code:

var coordinateTratte = doc.Descendants(ns + "Folder").First().Descendants(ns + "Folder")
    .Descendants(ns + "Placemark").Select(n =>              
    {
        string[] coordinates = n.Descendants(ns + "coordinates").First().Value.Split(' ');
        foreach (var coordinate in coordinates)
        {
            var coordinateLatLng = coordinate.Split(',');
            return new
            {
                latitude = coordinateLatLng.Last(),
                longitude = coordinateLatLng.First()
            };
        }
    });

and it says near n => that some values could not be expressed as Lambda expression.

Where am I wrong?

Upvotes: 2

Views: 127

Answers (1)

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 727097

The problem is that your lambda expression tries to return items "piecemeal" using a loop, while Select expects it to return the whole thing at once.

You can fix your code in several ways - for example, you could convert your foreach loop to a Select, and use SelectMany, like this:

var coordinateTratte = doc.Descendants(ns + "Folder").First().Descendants(ns + "Folder")
    .Descendants(ns + "Placemark").SelectMany(n =>
    { //                                 ^^^^
        string[] coordinates = n.Descendants(ns + "coordinates").First().Value.Split(' ');
        return coordinates
           .Select(coordinate => coordinate.Split(','))
           .Select(coordinateLatLng => new
            {
                latitude = coordinateLatLng.Last(),
                longitude = coordinateLatLng.First()
            });
    });

I want to return an object such as Dictionary<string,List<object>> where object is latitude and longitude

You can change the code like this:

var coordinateTratteDict = doc.Descendants(ns + "Folder").First().Descendants(ns + "Folder")
    .Descendants(ns + "Placemark").Select((n,i) =>
    {
        string[] coordinates = n.Descendants(ns + "coordinates").First().Value.Split(' ');
        return new {
            Index = i
        ,   CoordList = coordinates
           .Select(coordinate => coordinate.Split(','))
           .Select(coordinateLatLng => new
            {
                latitude = coordinateLatLng.Last(),
                longitude = coordinateLatLng.First()
            })
            .ToList()
        };
    })
    .ToDictionary(p => "Block_"+p.Index, p => p.CoordList);

Upvotes: 8

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