类文件

public static class WGS84ToGCJ02Helper
{
    // 定义一些常量
    private const double PI = 3.14159265358979324;
    private const double A = 6378245.0;
    private const double EE = 0.00669342162296594323;

    // 判断坐标是否在中国范围内（不在国内则不进行转换）
    private static bool OutOfChina(double lng, double lat)
    {
        return (lng < 72.004 || lng > 137.8347) ||
               (lat < 0.8293 || lat > 55.8271);
    }

    // 转换纬度
    private static double TransformLat(double x, double y)
    {
        double ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.Sqrt(Math.Abs(x));
        ret += (20.0 * Math.Sin(6.0 * x * PI) + 20.0 * Math.Sin(2.0 * x * PI)) * 2.0 / 3.0;
        ret += (20.0 * Math.Sin(y * PI) + 40.0 * Math.Sin(y / 3.0 * PI)) * 2.0 / 3.0;
        ret += (160.0 * Math.Sin(y / 12.0 * PI) + 320 * Math.Sin(y * PI / 30.0)) * 2.0 / 3.0;
        return ret;
    }

    // 转换经度
    private static double TransformLng(double x, double y)
    {
        double ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.Sqrt(Math.Abs(x));
        ret += (20.0 * Math.Sin(6.0 * x * PI) + 20.0 * Math.Sin(2.0 * x * PI)) * 2.0 / 3.0;
        ret += (20.0 * Math.Sin(x * PI) + 40.0 * Math.Sin(x / 3.0 * PI)) * 2.0 / 3.0;
        ret += (150.0 * Math.Sin(x / 12.0 * PI) + 300.0 * Math.Sin(x / 30.0 * PI)) * 2.0 / 3.0;
        return ret;
    }

    // WGS84 转 GCJ02
    public static (double lng, double lat) Wgs84ToGcj02(double wgsLng, double wgsLat)
    {
        if (OutOfChina(wgsLng, wgsLat))
        {
            return (wgsLng, wgsLat);
        }

        double dLat = TransformLat(wgsLng - 105.0, wgsLat - 35.0);
        double dLng = TransformLng(wgsLng - 105.0, wgsLat - 35.0);
        double radLat = wgsLat / 180.0 * PI;
        double magic = Math.Sin(radLat);
        magic = 1 - EE * magic * magic;
        double sqrtMagic = Math.Sqrt(magic);

        dLat = (dLat * 180.0) / ((A * (1 - EE)) / (magic * sqrtMagic) * PI);
        dLng = (dLng * 180.0) / (A / sqrtMagic * Math.Cos(radLat) * PI);

        double mgLat = wgsLat + dLat;
        double mgLng = wgsLng + dLng;

        return (mgLng, mgLat);
    }
}

调用

        // 示例：北京天安门的 WGS84 坐标
        double wgsLng = 116.397228;
        double wgsLat = 39.907501;
        
        // 转换为 GCJ02 坐标
        var gcjCoord = WGS84ToGCJ02Helper.Wgs84ToGcj02(wgsLng, wgsLat);
        
        Console.WriteLine($"WGS84 坐标: ({wgsLng}, {wgsLat})");
        Console.WriteLine($"GCJ02 坐标: ({gcjCoord.lng}, {gcjCoord.lat})");