C# 调用c库

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;

namespace test
{
public class CoordTrans
{
//
[DllImport("coord_trans.dll", EntryPoint = "convert", CallingConvention = CallingConvention.Cdecl)]
public static extern int convert(int from, int to, ref coord input, ref coord output);
}
public struct coord
{
/// <summary>维度</summary>
public double lat;
/// <summary>经度</summary>
public double lng;

/// <summary>坐标</summary>
/// <param name="lat">维度</param>
/// <param name="lng">经度</param>
public coord(double lat, double lng)
{
this.lat = lat;
this.lng = lng;
}
}

class Program
{
//取值为如下：
//1：GPS设备获取的角度坐标，wgs84坐标;
//3：google地图、soso地图、aliyun地图、mapabc地图和amap地图所用坐标，国测局坐标(GCJ02);
//5：百度地图采用的经纬度坐标(bd09ll);

static void Main(string[] args)
{
coord input = new coord(31.221816, 121.350051);
coord output = new coord(0.0, 0.0);
int result = CoordTrans.convert(1, 5, ref input, ref output);

if (result == 0)
Console.WriteLine("convert ok! lat[{0}], lng[{1}]", output.lat, output.lng);
else
Console.WriteLine("convert fail!");
}
}
}