'The specified input does not represent a valid geography instance' exception when using SqlGeographyBuilder

Question

I've written a small application that reads in from a series of KML files and then converts them into the Microsoft.SqlServer.Types.SqlGeography type using the following code:

    private SqlGeography CreateGeographyFromKML( string kml, bool debug )
    {
        // use SqlGeographyBuilder to help create the SqlGeography type 
        var geographyBuilder = new SqlGeographyBuilder();

        // Get co-ordinates 
        var xml = XDocument.Parse(kml);
        var df = xml.Root.Name.Namespace;
        XElement coordinates = xml.Descendants(df + "coordinates").Single();

        // set the Spatial Reference Identifiers that will used to create the point 
        geographyBuilder.SetSrid(_srid);
        geographyBuilder.BeginGeography(OpenGisGeographyType.Polygon);

        var longLat = coordinates.Value.Split(' ').Select(c => new { Lat = Convert.ToDouble(c.Split(',')[1]), Long = Convert.ToDouble(c.Split(',')[0]) });

        Console.Write("Found {0} ", longLat.Count());

        foreach (var coord in longLat.Select((x, i) => new { Index = i, Value = x }))
        {
            if (coord.Index == 0)
            { // First point
                if ( debug ) Console.WriteLine("First point: {0},{1}", coord.Value.Lat, coord.Value.Long);
                geographyBuilder.BeginFigure(coord.Value.Lat, coord.Value.Long);
            }
            else
            { // Intermediate points
                if (debug) Console.WriteLine("Intermediate point: {0},{1}", coord.Value.Lat, coord.Value.Long);
                geographyBuilder.AddLine(coord.Value.Lat, coord.Value.Long);
            }

            if (coord.Index == longLat.Count() - 1 )
            { // Last point (Close polygon)     
                if (debug) Console.Write("Last point: ");

                // Check not already added
                if (longLat.Last().Lat == longLat.First().Lat && longLat.Last().Long == longLat.First().Long)
                {
                    if (debug) Console.Write("Already exists - not adding...");
                }
                else
                {
                    if (debug) Console.Write("{0},{1}", longLat.Last().Lat, longLat.Last().Long);
                    geographyBuilder.AddLine(longLat.Last().Lat, longLat.Last().Long);
                }

                geographyBuilder.EndFigure(); // End figure
            }
        }

        if (debug) Console.WriteLine();

        // close the figure and geography class 
        geographyBuilder.EndGeography();

        // get the geography builder to return the sqlgeography type 
        return geographyBuilder.ConstructedGeography;
    }

Basically this code retrieves the list of Lat/Longs from the KML file, then loops through them to create a polygon.

However some of the KML files I'm importing fail with the following exception:

System.ArgumentException was caught Message=24200: The specified input does not represent a valid geography instance.

This happens on the following line: return geographyBuilder.ConstructedGeography;

I've found some reference to this exception, however in the cases I've found they're encountering and dealing with this exception within SQL Server, rather than C#.

Answer 1

I've had the same problem and solved it using a project called Sql Server Spatial Tools (http://sqlspatialtools.codeplex.com).

It has (among other interesting stuff) these two methods:

• MakeValidGeographyFromGeography
• MakeValidGeographyFromText (which receives a WKT string)

They modify the points so that it conforms to the geography restrictions.

It works really, really well, and I've used it for several months now without any problem.