Constructing entities from API with foreign keys

I'm loading three kinds of entities from an API (in csv format unfortunately). While the first two are fine, the third has foreign keys to both of them. What I'm currently doing is constructing the first two lists and then while constructing the third list I assign the entities for every item. This is how it looks:

var platforms = await Task.Run(() => parsed.Data.Select(p => CreatePlatform(p,stations,lines)).ToList());

private static Platform CreatePlatform(Dictionary data, List stations, List lines)
    {
        if (data.Keys.Except(PlatformFields).Any())
            return null; // TODO log; invalid data format
        Platform platform = null;
        try
        {
            platform = new Platform
            {
                SteigId = Convert.ToInt32(data["STEIG_ID"]),
                Richtung = data["RICHTUNG"],
                Reihenfolge = Convert.ToInt32(data["REIHENFOLGE"]),
                RblNummer = string.IsNullOrEmpty(data["RBL_NUMMER"]) ? null : (int?) Convert.ToInt32(data["RBL_NUMMER"]),
                Bereich = string.IsNullOrEmpty(data["BEREICH"])? null : (int?) Convert.ToInt32(data["BEREICH"]),
                Steig = data["STEIG"],
                SteigWgs84Lat = Convert.ToDouble(data["STEIG_WGS84_LAT"]),
                SteigWgs84Lon = Convert.ToDouble(data["STEIG_WGS84_LON"]),
                Stand = data["STAND"],

                Station = stations.Single(s => s.HaltestellenId == Convert.ToInt32(data["FK_HALTESTELLEN_ID"])),
                Line = lines.Single(l => l.LinienId == Convert.ToInt32(data["FK_LINIEN_ID"]))

            };
        }
        catch (FormatException ex)
        {
            return null; // TODO log;
        }
        return platform;
    }

Stations and Lines are sets that have been constructed in the exact same way (only without fk's). Hirarchy-wise I want the Stations to include a list of plattforms and each platform has the corresponding line. I also get this using the current method as entity frame

Using .Single() on an unsorted list has O(n) cost. If you use a data structure with constant time lookups e.g. a Dictionary and a Dictionary instead you should see a performance improvement using key lookup:

Station = stations[Convert.ToInt32(data["FK_HALTESTELLEN_ID"])],
Line = lines[Convert.ToInt32(data["FK_LINIEN_ID"])]

As you're using Single, I assumed that the dictionary will definitely contain the entry.

I don't know how you're creating your Lists but there is the Enumerable.ToDictionary method which could be useful:

var stationsLookup = stations.ToDictionary(s => s.HaltestellenId);

StackExchange Code Review Q#135578, answer score: 6