Reformat SQLGeography polygons to JSON

Question

I am building a web service that serves geographic boundary data in JSON format.

The geographic data is stored in an SQL Server 2008 R2 database using the geography type in a table. I use [ColumnName].ToString() method to return the polygon data as text.

Example output:

POLYGON ((-6.1646509904325884 56.435153006374627, ... -6.1606079906751 56.4338050060666))

MULTIPOLYGON (((-6.1646509904325884 56.435153006374627 0 0, ... -6.1606079906751 56.4338050060666 0 0)))

Geographic definitions can take the form of either an array of lat/long pairs defining a polygon or in the case of multiple definitions, an array or polygons (multipolygon).

I have the following regex that converts the output to JSON objects contained in multi-dimensional arrays depending on the output.

Regex latlngMatch = new Regex(@"(-?[0-9]{1}\.\d*)\s(\d{2}.\d*)(?:\s0\s0,?)?", RegexOptions.Compiled);

    private string ConvertPolysToJson(string polysIn)
    {
        return this.latlngMatch.Replace(polysIn.Remove(0, polysIn.IndexOf("(")) // remove POLYGON or MULTIPOLYGON
                                               .Replace("(", "[")  // convert to JSON array syntax
                                               .Replace(")", "]"), // same as above
                                               "{lng:$1,lat:$2},"); // reformat lat/lng pairs to JSON objects
    }

This is actually working pretty well and converts the DB output to JSON on the fly in response to an operation call.

However I am no regex master and the calls to String.Replace() also seem inefficient to me.

Does anyone have any suggestions/comments about performance of this?

Answer 1

Again just to just to close this off I will answer my own question with the solution im using.

This method takes the output from a ToString() call on an a MS SQL Geography Type. If the string returned contains polygon data contructed form GPS points, this method will parse and reformatted it to a JSON sting.

public static class PolyConverter
{
    static Regex latlngMatch = new Regex(@"(-?\d{1,2}\.\dE-\d+|-?\d{1,2}\.?\d*)\s(-?\d{1,2}\.\dE-\d+|-?\d{1,2}\.?\d*)\s?0?\s?0?,?", RegexOptions.Compiled);
    static Regex reformat = new Regex(@"\[,", RegexOptions.Compiled);

    public static string ConvertPolysToJson(string polysIn)
    {
        var formatted = reformat.Replace(
                        latlngMatch.Replace(
                        polysIn.Remove(0, polysIn.IndexOf("(")), ",{lng:$1,lat:$2}")
                        .Replace("(", "[")
                        .Replace(")", "]"), "[");

        if (polysIn.Contains("MULTIPOLYGON"))
        {
            formatted = formatted.Replace("[[", "[")
                                 .Replace("]]", "]")
                                 .Replace("[[[", "[[")
                                 .Replace("]]]", "]]");
        }

        return formatted;
    }
}

This is specific to my apllication, but maybe useful to somebody and maybe even create a better implementation.