从SQL Server地理数据类型在谷歌地图上显示多边形

AdamW的答案是正确的，但没有处理SqlGeography数据格式的数据。

包括对Microsoft.SqlServer.Types 的引用

SqlCommand cmd = new SqlCommand("SELECT STATEMENT",ConnectionString);
connectionString.Open();
SqlDataReader polygon = cmd.ExecuteReader();
While (polygon.read())
{
  string kmlCoordinates = string.Empty;
  SqlGeography geo = (SqlGeography)polygon["GeoColumn"];
  for(int i = 1; i <= geo.STNumPoints(); i++)
  {
       SqlGeography point = geo.STPointN(i);
       kmlCoordinates += point.Long + "," + point.Lat + " ";
  }
{
ConnectionString.Close();

注：地理点的索引是1，而不是0，而且它对foreach也不友好。

我过去曾使用KML文件在网页上覆盖多边形。

我建议阅读谷歌KML教程

• 创建一个从数据库中读取的函数
• 创建KML文件
• 从Google API调用KML文件

虽然KML为您提供了一种快速简单的覆盖形状的方法，但谷歌确实对显示的项目数量进行了限制。

以下内容将帮助您开始使用KML方法。

public ActionResult Kml()
    {
        DataAccess da = new DataAccess();
        string cellColor = "0032FB";
        string kml = @"<?xml version=""1.0"" encoding=""UTF-8""?>
        <kml xmlns=""http://earth.google.com/kml/2.1"">
            <Document>
                <Style id="polygon">
                    <LineStyle>
                        <color>FF" + cellColor + @"</color>
                    </LineStyle>
                    <PolyStyle>
                        <color>44" + cellColor +@"</color>
                        <fill>1</fill>
                        <outline>1</outline>
                    </PolyStyle> 
                </Style>
                <name>some name</name>
                <description>some des</description>
        ";
        DataTable polygons;
        foreach (DataRow polygon in polygons.Rows)
        {
                kml += @"
                    <Placemark>
                        <name>"somename @"</name>
                        <description><![CDATA[<p>some text</p>]]></description>" +
                        @"<styleUrl>#polygon</styleUrl>
                        <Polygon>
                            <extrude>1</extrude>
                            <altitudeMode>clampToSeaFloor</altitudeMode>
                            <outerBoundaryIs>
                                <LinearRing>
                                    <coordinates>" +
                                        polygon["Cell Limit  Longitude West"].ToString() + "," + polygon["Cell Limit Latitude North"].ToString() + " " +
                                        polygon["Cell Limit Longitude East"].ToString() + "," + polygon["Cell Limit Latitude North"].ToString() + " " +
                                        polygon["Cell Limit Longitude East"].ToString() + "," + polygon["Cell Limit Latitude South "].ToString() + " " +
                                        polygon["Cell Limit  Longitude West"].ToString() + "," + polygon["Cell Limit Latitude South "].ToString() + " " +
                                        polygon["Cell Limit  Longitude West"].ToString() + "," + polygon["Cell Limit Latitude North"].ToString() + " " +
                                    @"</coordinates>
                                </LinearRing>
                            </outerBoundaryIs>
                        </Polygon>
                    </Placemark>
                ";
        }
        kml += @"</Document>
        </kml>";
        byte[] data = Encoding.ASCII.GetBytes(kml);
        return File(data, "application/vnd.google-earth.kml+xml", id);
    }

Javascript

var url = 'http://www.example.com/AppName/GMap/file.kml &rand=' + Math.random();
layer_paperCharts = new google.maps.KmlLayer(url);
if (loadedonce) {
  layer_paperCharts.set('preserveViewport', true);
} else {
  loadedonce = true;
}
layer_paperCharts.setMap(map);

Google缓存KML文件，因此添加Math.random（）可以解决这个问题。

您也可以查看Fusion Tables。但是你必须上传你的数据到谷歌。此外，谷歌还对所提供的数据进行了分组。但是您需要SQL，因此此选项可能不可用。

    public void KmlExport()
    {
        string cellColor = "COLOR";
        string KMLname = "KML NAME";
        string description = "KML DESCRIPTION";
        string kml = @"<?xml version=""1.0"" encoding=""UTF-8""?>
                        <kml xmlns=""http://www.opengis.net/kml/2.2"">
                            <Document>
                                <Style id=""polygon"">
                                    <LineStyle>
                                        <color>FF" + cellColor + @"</color>
                                    </LineStyle>
                                    <PolyStyle>
                                        <color>44" + cellColor + @"</color>
                                        <fill>1</fill>
                                        <outline>1</outline>
                                    </PolyStyle> 
                                </Style>
                                <name>" + KMLname + @"</name>
                                <description>" + description + "</description>";
        SqlCommand cmd = new SqlCommand("Select Statement", connectionString);
        cs.Open();
        SqlDataReader polygon = cmd.ExecuteReader();
        while (polygon.Read())
        {
            string kmlCoordinates = string.Empty;
            SqlGeography geo = (SqlGeography)polygon["GEOGRAPHY COLUMN"];
                for (int i = 1; i <= geo.STNumPoints(); i++)
                {
                    SqlGeography point = geo.STPointN(i);
                    kmlCoordinates += point.Long + "," + point.Lat + " ";
                }
                string polyName = polygon["Name Column"].ToString();
                string polyDescription = polygon["Description Column"].ToString();
                kml += @"
                <Placemark>
                    <name>" + polyName + @"</name>
                    <description><![CDATA[<p>" + polyDescription + "</p>]]></description>" +
                        @"<styleUrl>#polygon</styleUrl>
                    <Polygon>
                        <extrude>1</extrude>
                        <altitudeMode>clampToSeaFloor</altitudeMode>
                        <outerBoundaryIs>
                            <LinearRing>
                                <coordinates>" + kmlCoordinates +
                              @"</coordinates>
                            </LinearRing>
                        </outerBoundaryIs>
                    </Polygon>
                </Placemark>";
                kmlCoordinates = string.Empty;
            }
        cs.Close();
        kml += @"</Document></kml>";
        StreamWriter file = new StreamWriter(@"OUTPUTFILE.KML");
        file.WriteLine(kml);
        file.Close();

这是Adam W和Blair M的解决方案的结合。我修改了它，这样如果数据库中有多个多边形，就会生成KML文件。