iOS平台MAUI项目API传参时出现无效坐标问题

问题现象 #

当前API方法在Android平台运行正常，但iOS平台下传递double类型坐标时，小数点会丢失。例如传入纬度26.590354、经度49.972707，服务器端接收到的是26590354和49972707，导致坐标无效；但直接在GetStringAsync中写死字符串坐标则可正常运行。

问题原因 #

iOS系统的区域设置可能默认使用逗号作为小数分隔符，当double类型变量自动转换为字符串时，会将小数点替换为逗号。拼接URL后，服务器解析时会忽略逗号，导致数字被错误解析为无小数点的整数。

解决方案 #

方案1：强制使用不变文化格式化坐标 #

通过CultureInfo.InvariantCulture显式指定格式化规则，确保double转字符串时始终使用小数点作为分隔符：

using System.Globalization;

public static async Task<List<Shop>> GetShops(double customerLat, double customerLong)
{
    var httpClient = new HttpClient();
    httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("bearer", Preferences.Get("accessToken", string.Empty));
    
    // 用不变文化格式化坐标，避免区域设置影响
    var latStr = customerLat.ToString(CultureInfo.InvariantCulture);
    var longStr = customerLong.ToString(CultureInfo.InvariantCulture);
    
    var response = await httpClient.GetStringAsync($"{AppSettings.ApiUrl}api/Shops?userLat={latStr}&userLong={longStr}");
    return JsonConvert.DeserializeObject<List<Shop>>(response);
}

方案2：使用查询参数构建工具（更安全） #

借助HttpUtility.ParseQueryString构建查询参数，自动处理格式编码问题，避免手动拼接URL的潜在错误：

using System.Globalization;
using System.Web;

public static async Task<List<Shop>> GetShops(double customerLat, double customerLong)
{
    var httpClient = new HttpClient();
    httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("bearer", Preferences.Get("accessToken", string.Empty));
    
    var queryString = HttpUtility.ParseQueryString(string.Empty);
    queryString.Add("userLat", customerLat.ToString(CultureInfo.InvariantCulture));
    queryString.Add("userLong", customerLong.ToString(CultureInfo.InvariantCulture));
    
    var url = $"{AppSettings.ApiUrl}api/Shops?{queryString}";
    var response = await httpClient.GetStringAsync(url);
    return JsonConvert.DeserializeObject<List<Shop>>(response);
}

内容的提问来源于stack exchange，提问作者Ali Alfaraj