随笔背景：因为项目中有个简单的功能是需要实现中文简体到繁体的切换，数据库中存储的源数据都是中文简体的，为了省事就想着通过HttpHeader的方式来控制Api返回对应的繁体数据。
实现方式：通过Asp.Net Core 中的中间件来拦截HttpResponse，然后通过转换字符编码来实现中文繁体切换。
实现代码如下：
HttpContextMiddleware 中间件
public class HttpContextMiddleware ???{ ???????private readonly RequestDelegate _next; ???????public HttpContextMiddleware(RequestDelegate next) ???????{ ???????????_next = next; ???????} ???????public async Task Invoke(HttpContext context) ???????{ ???????????var originalBodyStream = context.Response.Body; ???????????????????????using (var responseBody = new MemoryStream()) ???????????{ ???????????????context.Response.Body = responseBody; ???????????????await _next(context); ???????????????var result = await FormatResponse(context.Response); ???????????????if (context.Request.Headers.Keys.Contains(Constants.HttpHeaderLanguage)) ???????????????{ ???????????????????var lang = context.Request.Headers.GetCommaSeparatedValues(Constants.HttpHeaderLanguage).GetValue(0).ToString(); ??????????????????????????????if (lang == "zh-tw") ???????????????????{ ???????????????????????var traditionresult = ConvertHelper.ToTraditional(result); ???????????????????????byte[] array = Encoding.UTF8.GetBytes(traditionresult); ???????????????????????MemoryStream stream = new MemoryStream(array); ???????????????????????try ???????????????????????{ ???????????????????????????await stream.CopyToAsync(originalBodyStream); ???????????????????????} ???????????????????????catch (Exception ex) ???????????????????????{ ???????????????????????????throw ex; ???????????????????????} ???????????????????} ???????????????????else ???????????????????{ ???????????????????????try ???????????????????????{ ???????????????????????????await responseBody.CopyToAsync(originalBodyStream); ???????????????????????} ???????????????????????catch (Exception ex) ???????????????????????{ ???????????????????????????throw ex; ???????????????????????} ???????????????????} ???????????????} ???????????????else ???????????????{ ???????????????????await responseBody.CopyToAsync(originalBodyStream); ???????????????} ???????????} ???????} ???????private async Task<string> FormatResponse(HttpResponse response) ???????{ ???????????response.Body.Seek(0, SeekOrigin.Begin); ???????????var text = await new StreamReader(response.Body).ReadToEndAsync(); ???????????response.Body.Seek(0, SeekOrigin.Begin); ???????????return $"{text}"; ???????} ???}Startup.cs
public void Configure(IApplicationBuilder app, IHostingEnvironment env) ??????{ ???????????app.UseDefaultFiles(); ???????????app.UseAuthentication(); ???????????app.UseStaticFiles(); ???????????//在Mvc之前注入到管道中 ???????????app.UseMiddleware<HttpContextMiddleware>(); ???????????app.UseMvc(); ???????????}ConvertHelper 中文简体繁体转换工具类
public static ?class ConvertHelper ?{ ???????private const int LOCALE_SYSTEM_DEFAULT = 0x0800; ???????private const int LCMAP_SIMPLIFIED_CHINESE = 0x02000000; ???????private const int LCMAP_TRADITIONAL_CHINESE = 0x04000000; ???????[DllImport("kernel32", CharSet = CharSet.Auto, SetLastError = true)] ???????private static extern int LCMapString(int Locale, int dwMapFlags, string lpSrcStr, int cchSrc, [Out] string lpDestStr, int cchDest); ???????/// <summary> ???????/// 将字符转换成简体中文 ???????/// </summary> ???????/// <param name="source">输入要转换的字符串</param> ???????/// <returns>转换完成后的字符串</returns> ???????public static string ToSimplified(string source) ???????{ ???????????String target = new String(‘ ‘, source.Length); ???????????int ret = LCMapString(LOCALE_SYSTEM_DEFAULT, LCMAP_SIMPLIFIED_CHINESE, source, source.Length, target, source.Length); ???????????return target; ???????} ???????/// <summary> ???????/// 将字符转换为繁体中文 ???????/// </summary> ???????/// <param name="source">输入要转换的字符串</param> ???????/// <returns>转换完成后的字符串</returns> ???????public static string ToTraditional(string source) ???????{ ???????????String target = new String(‘ ‘, source.Length); ???????????int ret = LCMapString(LOCALE_SYSTEM_DEFAULT, LCMAP_TRADITIONAL_CHINESE, source, source.Length, target, source.Length); ???????????return target; ???????} ???}以上源代码就是所有关键代码了，中间件注入以后，不用再在action里或controller里单独拦截，经测试，会拦截所有api的响应结果。这里有个插曲是我之前尝试过使用ResultFilter来拦截，但没法做到在响应后拦截响应结果。不知出于什么原因，最后我放弃了Filter的方式，选择了这种中间件的拦截方式。
本文参考如下：
https://elanderson.net/2017/02/log-requests-and-responses-in-asp-net-core/
本文如有不对的地方，欢迎指正！愿与君共勉。
最后，感谢您的阅读！
Asp.Net Core 2.0实现HttpResponse中繁切换
原文地址：https://www.cnblogs.com/valuemar/p/9375149.html