Answer to [stackoverflow question](http://stackoverflow.com/questions/19567990/how-to-pass-c-sharp-datatable-to-a-javascript-function)

GetJsonCollectionFromDataTable.cs

using System;
using System.Collections.Generic;
using System.Data;

namespace GetJsonCollectionFromDataTable
{
    class Program
    {
        static void Main()
        {
            var indexOfColumnNames = new Dictionary<int, string>();
            
            indexOfColumnNames.Add(5, "title");
            indexOfColumnNames.Add(9, "lat");
            indexOfColumnNames.Add(10, "lng");
            indexOfColumnNames.Add(11, "description");


            var columnsAreNotStringType = new List<string>() { "lat", "lng" };

            var length = 4; //Get the first 'n' elements
            var dummyDataTable = CreateDummyTable();


            var jsonCollection = CreateJsonCollection(dummyDataTable, indexOfColumnNames, columnsAreNotStringType, length);

            Console.WriteLine(jsonCollection);
            Console.ReadLine();
        }

        private static string CreateJsonCollection(DataTable dataTable, Dictionary<int, string> indexAndColumnNames, List<string> columnsAreNotStringType, int length)
        {
            var preJsonCollection = new List<string>();

            for (int rowIndex = 0; rowIndex < length; rowIndex++)
                preJsonCollection.Add(CreateJsonObjectFromRow(dataTable.Rows[rowIndex], indexAndColumnNames, columnsAreNotStringType));


            return string.Format("[{0}]", string.Join(",", preJsonCollection));
        }
        
        private static DataTable CreateDummyTable()
        {
            var dummyDataTable = new DataTable();

            for (int i = 0; i < 12; i++)
                dummyDataTable.Columns.Add(new DataColumn());

            var dummyDataRow1 = dummyDataTable.NewRow();
            dummyDataRow1[5] = "via Andria, Roma";
            dummyDataRow1[9] = 41.8902643;
            dummyDataRow1[10] = 12.6638589;
            dummyDataRow1[11] = "fdsad";

            var dummyDataRow2 = dummyDataTable.NewRow();
            dummyDataRow2[5] = "via canosa, Roma";
            dummyDataRow2[9] = 41.8838417;
            dummyDataRow2[10] = 12.5438227;
            dummyDataRow2[11] = "fdsad";

            var dummyDataRow3 = dummyDataTable.NewRow();
            dummyDataRow3[5] = "via taranto, Milano";
            dummyDataRow3[9] = 45.4383343;
            dummyDataRow3[10] = 9.1505354;
            dummyDataRow3[11] = "fdsad";

            var dummyDataRow4 = dummyDataTable.NewRow();
            dummyDataRow4[5] = "via barletta, Roma";
            dummyDataRow4[9] = 41.9102707;
            dummyDataRow4[10] = 12.4580826;
            dummyDataRow4[11] = "fdsad";


            dummyDataTable.Rows.Add(dummyDataRow1);
            dummyDataTable.Rows.Add(dummyDataRow2);
            dummyDataTable.Rows.Add(dummyDataRow3);
            dummyDataTable.Rows.Add(dummyDataRow4);

            return dummyDataTable;
        }

        private static string CreateJsonObjectFromRow(DataRow dataRow, Dictionary<int, string> indexAndColumnNames, List<string> columnsAreNotStringType)
        {            
            var tmpPreJsonObject = new List<string>(indexAndColumnNames.Count);

            foreach (var indexNamePair in indexAndColumnNames)
            {
                var columnName = indexNamePair.Value;
                var columnIndex = indexNamePair.Key;
                var formatedString = columnsAreNotStringType.Contains(columnName) ? "\"{0}\" : {1}" : "\"{0}\" : \"{1}\"";

                tmpPreJsonObject.Add(string.Format(formatedString, columnName, dataRow[columnIndex]));
            }

            return string.Format("{{{0}}}", string.Join(",", tmpPreJsonObject));
        }
    }
}