自定义中间件（MiddleWare）

原文链接： https://www.cnblogs.com/ysmc/p/16512669.html

　　以下代码自定义简单的异常处理中间件Demo

ExceptionMiddleWare

 1 public class ExceptionMiddleWare
 2 {
 3     private readonly RequestDelegate _next;
 4     public ExceptionMiddleWare(RequestDelegate next)
 5     {
 6         _next = next;
 7     }
 8     public async Task Invoke(HttpContext context)
 9     {
10         try
11         {
12             await _next.Invoke(context);
13         }
14         catch (Exception ex)
15         {
16             await HandleExceptionAsync(context, ex);
17         }
18     }
19     private async Task HandleExceptionAsync(HttpContext context, Exception exception)
20     {
21         var time = DateTime.Now.ToString("yyyyMMddhhmmss");
22         FileHelper.WriteInformationFile(exception.ToString(), Path.Combine("Errlog", DateTime.Now.ToString("yyyyMMdd"), time + ".txt"));
23         var response = context.Response;
24         response.ContentType = "application/json";
25         response.StatusCode = (int)HttpStatusCode.InternalServerError;
26         await response.WriteAsync(JsonConvert.SerializeObject(new
27         {
28             // customize as you need
29             error = new
30             {
31                 message = "系统错误，请联系管理员",
32                 errfile = time
33             }
34         }));
35     }
36 }

ExceptionMiddleWareBuilder

public static class ExceptionMiddleWareBuilder
{
    public static IApplicationBuilder ExceptionMiddleWare(this IApplicationBuilder builder) => builder.UseMiddleware<ExceptionMiddleWare>();
}

Startup

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    app.HttpRequestMiddleWare();

    if (env.IsDevelopment())
    {
        //app.UseDeveloperExceptionPage();
        app.ExceptionMiddleWare();
    }
    else
        app.ExceptionMiddleWare();

    app.UseMvc();
}