how to set the output type List<string> in a middleware in .NET Core 2.1? - asp.net-core

Question

I have this middleware class when I want to show a List<string> in the output:
namespace WebAspNetCore2_1
{
public class LearningMiddleware
{
private readonly RequestDelegate _next;
private readonly ILogger<LearningMiddleware> _logger_log;
private readonly List<string> logger;
public LearningMiddleware(RequestDelegate next,ILogger<LearningMiddleware> logger_log)
{
_next = next;
_logger_log = logger_log;
List<string> _logger = new List<string>
{
("EUR/USD"),
("1.0500")
};
logger = _logger;
}
public Task Invoke(HttpContext httpContext)
{
_logger_log.Log(Microsoft.Extensions .Logging.LogLevel.Information,"information of logger",logger[0]);
return _next(httpContext);
}
}
}
I have debugged my code but seen to be correct, my List<> is filled, I don't know why the compiler is throwing this exception:
InvalidOperationException: Could not create an instance of type Microsoft.Extensions.Logging.ILogger`1[[System.String, System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]'. Model bound complex types must not be abstract or value types and must have a parameterless constructor. Alternatively, give the 'logger' parameter a non-null default value.
i thought was the order declaration in StartUp, but not
public void ConfigureServices(IServiceCollection services)
{
services.Configure<CookiePolicyOptions>(options =>
{
// This lambda determines whether user consent for non-essential cookies is needed for a given request.
options.CheckConsentNeeded = context => true;
options.MinimumSameSitePolicy = SameSiteMode.None;
});
services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
// app.UseLearningMiddleware();
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
else
{
app.UseExceptionHandler("/Error");
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseCookiePolicy();
app.UseMiddleware<LearningMiddleware>();
app.UseMvc();
}
link in video for detail evidence: https://youtu.be/2FoLvhLweYo

Answer 1

I tested your code in my side but it worked well... I created a new asp.net core 2.1 MVC project and create a middleware. In StartUp.cs, I put app.UseMiddleware<MyMiddleware>(); just before app.UseMvc(routes =>
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using System.Collections.Generic;
using System.Threading.Tasks;
namespace WebApplication2
{
// You may need to install the Microsoft.AspNetCore.Http.Abstractions package into your project
public class MyMiddleware
{
private readonly RequestDelegate _next;
private readonly ILogger<MyMiddleware> _logger_log;
private readonly List<string> logger;
public MyMiddleware(RequestDelegate next, ILogger<MyMiddleware> logger_log)
{
_next = next;
_logger_log = logger_log;
List<string> _logger = new List<string>
{
("EUR/USD"),
("1.0500")
};
logger = _logger;
}
public Task Invoke(HttpContext httpContext)
{
_logger_log.Log(Microsoft.Extensions.Logging.LogLevel.Information, "information of logger", logger[0]);
return _next(httpContext);
}
}
// Extension method used to add the middleware to the HTTP request pipeline.
public static class MyMiddlewareExtensions
{
public static IApplicationBuilder UseMyMiddleware(this IApplicationBuilder builder)
{
return builder.UseMiddleware<MyMiddleware>();
}
}
}