using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using ThinkGeo.MapSuite.Core;
namespace GreatCircleWithGoogleMap
{
    //This class, inheriting from Projection, applies the very simple projection of offsetting all the points
    //360 degrees to the left.
    class OffsetProjection: Projection, IDisposable
    {
        public double offset; // = 20026376.393709917 * 2;//20037503; //360
        protected override Vertex[] ConvertToExternalProjectionCore(double[] x, double[] y)
        {
            Vertex[] vertices = new Vertex[x.Length];
            for (int i = 0; i < vertices.Length; i++)
            {
                vertices[i] = new Vertex(x[i] - offset , y[i]);
            }
            return vertices;
        }
        protected override Vertex[] ConvertToInternalProjectionCore(double[] x, double[] y)
        {
            Vertex[] vertices = new Vertex[x.Length];
            for (int i = 0; i < vertices.Length; i++)
            {
                vertices[i] = new Vertex(x[i] + offset, y[i]);
            }
            return vertices;
        }
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
        private void Dispose(bool disposing)
        {
            Close();
        }
    }
}

using System;
using System.Configuration;
using ThinkGeo.MapSuite.Core;
using ThinkGeo.MapSuite.WebEdition;
namespace GreatCircleWithGoogleMap
{
    public partial class TestForm : System.Web.UI.Page
    {
        enum OffsetType { OffsetWest, OffsetEast }
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!Page.IsPostBack)
            {
                Map1.MapBackground.BackgroundBrush = new GeoSolidBrush(GeoColor.FromHtml("#E5E3DF"));
                Map1.CurrentExtent = new RectangleShape(-27663034,9063122,-10064167,-468782);
                Map1.MapUnit = GeographyUnit.Meter;
                Map1.MapTools.OverlaySwitcher.Enabled = true;
                Map1.MapTools.MouseCoordinate.Enabled = true;
                //Adds the Google Map as an overlay
                GoogleOverlay google = new GoogleOverlay("Google Map");
                google.JavaScriptLibraryUri = new Uri(ConfigurationManager.AppSettings["GoogleUri"]);
                google.GoogleMapType = GoogleMapType.Normal;
                Map1.CustomOverlays.Add(google);
                LayerOverlay layerOverlay = new LayerOverlay("PointOverlay", false, TileType.SingleTile);
                layerOverlay.TransitionEffect = TransitionEffect.None;
                //Projection to go from Geodetic to Google Map projection.
                Proj4Projection proj4 = new Proj4Projection();
                proj4.InternalProjectionParametersString = Proj4Projection.GetEpsgParametersString(4326);
                proj4.ExternalProjectionParametersString = Proj4Projection.GetGoogleMapParametersString();
                //Longitude1 = -93.697919536597226
                //Latitude1=  47.9236905227374
                //Longitude2  = 37.549353522156949
                //Latitude2 = 37.660395791749444
                //Display the feature for Los Angeles simply projecting from Geodetic to Google map projection.
                double Longitude1 = -118.55; //-93.697919536597226; //  //
                double Latitude1 = 34.08; //47.9236905227374;  //
                proj4.Open();
                Vertex googleMapLAVertex = proj4.ConvertToExternalProjection(Longitude1, Latitude1);
                PointShape LA_Point = new PointShape(googleMapLAVertex);
                //Display the feature for Shanghai by projecting from Geodetic to Google map projection and then by using offseting projection.
                double Longitude2 = 121.78; //37.549353522156949; //
                double Latitude2 = 31.01; //37.660395791749444; //
                Vertex googleMapSVertex = proj4.ConvertToExternalProjection(Longitude2, Latitude2);
                OffsetProjection offsetProj = new OffsetProjection();
                //Calculates what 360 degrees of offset corresponds to the Google projection for the offset value
                Vertex offsetVertexReference = proj4.ConvertToExternalProjection(180, 0);
                offsetProj.offset = - offsetVertexReference.X * 2;
                offsetProj.Open();
                Vertex offsetVertex = offsetProj.ConvertToExternalProjection(googleMapSVertex.X,googleMapSVertex.Y);
                offsetProj.Close();
                PointShape S_Point = new PointShape(offsetVertex); //(googleMapSVertex); //offsetVertex);
                Feature GPSFeature = new Feature(LA_Point);
                Feature GPSFeature2 = new Feature(S_Point);
                InMemoryFeatureLayer pointLayer = new InMemoryFeatureLayer();
                pointLayer.InternalFeatures.Add(GPSFeature2);
                pointLayer.InternalFeatures.Add(GPSFeature);
                pointLayer.ZoomLevelSet.ZoomLevel01.DefaultPointStyle = PointStyles.CreateSimplePointStyle(PointSymbolType.Square,
                                                                        GeoColor.StandardColors.Red, GeoColor.StandardColors.Black, 2, 20);
                pointLayer.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level20;
                //InMemoryFeatureLayer for the Great Circle.
                InMemoryFeatureLayer GreatCircle = new InMemoryFeatureLayer();
                GreatCircle.ZoomLevelSet.ZoomLevel01.DefaultLineStyle = LineStyles.CreateSimpleLineStyle(GeoColor.SimpleColors.Red, 3, true);
                GreatCircle.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level20;
                //The great circle requires to have the part being in the eastern hemisphere to be offset to the left
                // so that it display on the pacific rim.
                //We need to pass the points in decimal degrees.
                MultilineShape greatCircleMultiLineShape = GetGreatCircle(new PointShape(Longitude1, Latitude1), new PointShape(Longitude2, Latitude2),OffsetType.OffsetWest);
                Feature GreatCirclefeature = new Feature(greatCircleMultiLineShape);
                GreatCircle.InternalFeatures.Add("Great Circle", GreatCirclefeature);
                layerOverlay.Layers.Add(pointLayer);
                layerOverlay.Layers.Add(GreatCircle);
                Map1.CustomOverlays.Add(layerOverlay);
             }
        }
        private MultilineShape GetGreatCircle(PointShape pointShape1, PointShape pointShape2, OffsetType offsetType)
        {
            //Projection from Geodetic to Google Map.
            Proj4Projection proj4 = new Proj4Projection();
            proj4.InternalProjectionParametersString = Proj4Projection.GetEpsgParametersString(4326);
            proj4.ExternalProjectionParametersString = Proj4Projection.GetGoogleMapParametersString();
            //Offset projection for Google map.
            OffsetProjection offsetGoogleProj = new OffsetProjection();
            proj4.Open();
            Vertex offsetVertexReference = proj4.ConvertToExternalProjection(180, 0);
            if (offsetType == OffsetType.OffsetWest)
            {
                offsetGoogleProj.offset = offsetVertexReference.X * 2;
            }
            else
            {
                offsetGoogleProj.offset = -offsetVertexReference.X * 2;
            }
            offsetGoogleProj.Open();
            //Gets the Great Circle in decimal degrees.
            MultilineShape greatCircleMultiLineShape = pointShape1.GetShortestLineTo(pointShape2, GeographyUnit.DecimalDegree);
            //Builds the MultilineShape in the Google Map projection.
            MultilineShape resultGreatMultiLineShape = new MultilineShape();
            if (greatCircleMultiLineShape.Lines.Count > 1)
            {
                foreach (LineShape lineShape in greatCircleMultiLineShape.Lines)
                {
                    if (lineShape.Vertices[0].X < 0)
                    {
                        LineShape resultLineShape = new LineShape();
                        if (offsetType == OffsetType.OffsetWest)
                        {
                            foreach (Vertex vertex in lineShape.Vertices)
                            {
                                Vertex projVertex = proj4.ConvertToExternalProjection(vertex.X, vertex.Y);
                                resultLineShape.Vertices.Add(projVertex);
                            }
                        }
                        else
                        {
                            foreach (Vertex vertex in lineShape.Vertices)
                            {
                                Vertex projVertex = proj4.ConvertToExternalProjection(vertex.X, vertex.Y);
                                Vertex offsetVertex = offsetGoogleProj.ConvertToExternalProjection(projVertex.X, projVertex.Y);
                                resultLineShape.Vertices.Add(offsetVertex);
                            }
                        }
                        resultGreatMultiLineShape.Lines.Add(resultLineShape);
                    }
                    else
                    {
                        LineShape resultLineShape = new LineShape();
                        if (offsetType == OffsetType.OffsetWest)
                        {
                            foreach (Vertex vertex in lineShape.Vertices)
                            {
                                Vertex projVertex = proj4.ConvertToExternalProjection(vertex.X, vertex.Y);
                                Vertex offsetVertex = offsetGoogleProj.ConvertToExternalProjection(projVertex.X, projVertex.Y);
                                resultLineShape.Vertices.Add(offsetVertex);
                            }
                        }
                        else
                        {
                            foreach (Vertex vertex in lineShape.Vertices)
                            {
                                Vertex projVertex = proj4.ConvertToExternalProjection(vertex.X, vertex.Y);
                                resultLineShape.Vertices.Add(projVertex);
                            }
                        }
                        resultGreatMultiLineShape.Lines.Add(resultLineShape);
                    }
                }
            }
            else
            {
                LineShape resultLineShape = new LineShape();
                foreach (Vertex vertex in greatCircleMultiLineShape.Lines[0].Vertices)
                {
                    Vertex projVertex = proj4.ConvertToExternalProjection(vertex.X, vertex.Y);
                    resultLineShape.Vertices.Add(projVertex);
                }
                resultGreatMultiLineShape.Lines.Add(resultLineShape);
            }
            proj4.Close();
            offsetGoogleProj.Close();
            return resultGreatMultiLineShape;
        }
    }
}

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="TestForm.aspx.cs" Inherits="GreatCircleWithGoogleMap.TestForm" %>
<%@ Register Assembly="WebEdition" Namespace="ThinkGeo.MapSuite.WebEdition" TagPrefix="cc1" %>
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <link href="~/theme/default/samplepic/style.css" rel="stylesheet" type="text/css" />
    <title>Great Circle on Google Map</title>
</head>
<body>
    <form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
    <cc1:Map ID="Map1" runat="server" Height="100%" Width="100%">
    </cc1:Map>
   <%-- <description:descriptionpanel ID="DescPanel" runat="server">
        This sample displays a google map. Click buttons below to switch between different Google maps.
        <br />
        <br />
        <asp:Button CssClass="btn" ID="btnRoad" runat="server" Text="Normal" OnClientClick="Map1.SetCurrentBackgroundMapType(G_NORMAL_MAP); return false;" />
        <asp:Button CssClass="btn" ID="btnAerial" runat="server" Text="Hybrid" OnClientClick="Map1.SetCurrentBackgroundMapType(G_HYBRID_MAP); return false;" /><br />
        <asp:Button CssClass="btn" ID="btnSatellite" runat="server" Text="Satellite" OnClientClick="Map1.SetCurrentBackgroundMapType(G_SATELLITE_MAP); return false;" />
        <asp:Button CssClass="btn" ID="btnPhysical" runat="server" Text="Physical" OnClientClick="Map1.SetCurrentBackgroundMapType(G_PHYSICAL_MAP); return false;" />
    </description:descriptionpanel>--%>
    </form>
</body>
</html>