希望 ASP.NET Core 中间件在 MVC Razor View Engine 之后运行

Question

我希望在 MVC Razor View Engine 处理数据后在 ASP.NET Core 中运行中间件模块。 我可以让它运行，但它似乎没有收集所有数据。 我有一个标记帮助程序，可以更新 DI 对象的集合，但是当中间件运行时，DI 对象的集合为空。 我的startup.cs看起来像这样：

    public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
    { 
        loggerFactory.AddConsole(Configuration.GetSection("Logging"));
        loggerFactory.AddDebug();

        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
            app.UseBrowserLink();
        }
        else
        {
            app.UseExceptionHandler("/Home/Error");
        }

        app.UseStaticFiles();

        app.UseMiddleware<MyMiddleware>();

        app.UseMvc(routes =>
        {
            routes.MapRoute(
                name: "default",
                template: "{controller=Home}/{action=Index}/{id?}");
        });
    }

我的中间件是这样的：

public class MyMiddleware
{
    private readonly RequestDelegate nextMiddleware;
    private readonly IScriptManager _scriptManager;

    public MyMiddleware(RequestDelegate next, IScriptManager scriptManager)
    {
        this.nextMiddleware = next;
        _scriptManager = scriptManager;
    }

    public async Task Invoke(HttpContext context)
    {
        var cnt = _scriptManager.ScriptTexts.Count;
        .. get HTML
        Stream originalStream = context.Response.Body;
        ...
        .. update HTML
        await context.Response.WriteAsync(htmlData);

我确实得到了我想要的 HTML，但我的 DI 中的集合似乎没有更新。

*** 注释 - 可能但不起作用的结果过滤器

        services.AddMvc(options =>
        {
            options.Filters.Add(new AppendToHtmlBodyFilter());
        });

public class AppendToHtmlBodyFilter : TypeFilterAttribute
{
    private readonly IScriptManager _scriptManager;

    public AppendToHtmlBodyFilter():base(typeof(SampleActionFilterImpl))
    {
    }

    private class SampleActionFilterImpl : IResultFilter
    {
        private readonly IScriptManager _scriptManager;

        public SampleActionFilterImpl(IScriptManager scriptManager)
        {
            _scriptManager = scriptManager;
            //_logger = loggerFactory.CreateLogger<SampleActionFilterAttribute>();
        }

        public void OnResultExecuted(ResultExecutedContext context)
        {
            var cnt = _scriptManager.ScriptTexts.Count;
            Stream originalStream = context.HttpContext.Response.Body;
            using (MemoryStream newStream = new MemoryStream())
            {
                context.HttpContext.Response.Body = newStream;
                context.HttpContext.Response.Body = originalStream;
                newStream.Seek(0, SeekOrigin.Begin);
                StreamReader reader = new StreamReader(newStream);
                var htmlData = reader.ReadToEnd();

Answer 1

据我所知，在请求管道中的 mvc 之后无法运行中间件。如果您想操纵剃刀输出，可以使用过滤器。结果过滤器似乎适合您的情况。

结果过滤器非常适合任何需要直接包围的逻辑 查看执行或格式化程序执行。结果过滤器可以替换或 修改负责产生的操作结果 回应。

参见官方文档https://learn.microsoft.com/en-us/aspnet/core/mvc/controllers/filters#result-filters

另请参阅如何使用过滤器进行依赖注入https://learn.microsoft.com/en-us/aspnet/core/mvc/controllers/filters#dependency-injection

更新

我无法让它与结果过滤器一起工作（它可以工作 json 结果，但不能工作 viewresult）。

但是我发现了一个很好的中间件示例：http://www.mikesdotnetting.com/article/269/asp-net-5-middleware-or-where-has-my-httpmodule-gone

public class MyMiddleware
{
    private readonly RequestDelegate nextMiddleware;
    private readonly IScriptManager _scriptManager;

    public MyMiddleware(RequestDelegate next, IScriptManager scriptManager)
    {
       this.nextMiddleware = next;
       _scriptManager = scriptManager;
    }
    public async Task Invoke(HttpContext context)
    {
       var cnt = _scriptManager.ScriptTexts.Count;
        using (var memoryStream = new MemoryStream())
        {
            var bodyStream = context.Response.Body;
            context.Response.Body = memoryStream;

            await _next(context);

            var isHtml = context.Response.ContentType?.ToLower().Contains("text/html");
            if (context.Response.StatusCode == 200 && isHtml.GetValueOrDefault())
            {
                    memoryStream.Seek(0, SeekOrigin.Begin);
                    using (var streamReader = new StreamReader(memoryStream))
                    {
                        var responseBody = await streamReader.ReadToEndAsync();
                        // update html
                        using (var amendedBody = new MemoryStream())
                        using (var streamWriter = new StreamWriter(amendedBody))
                        {
                            streamWriter.Write(responseBody);
                            amendedBody.Seek(0, SeekOrigin.Begin);
                            await amendedBody.CopyToAsync(bodyStream);
                        }
                    }
            }
        }
    }
}

Answer 2

对于其他遇到此问题想知道如何做到这一点的人。您可以通过在中间件的

nextMiddleware

方法中的代码之前调用

InvokeAsync

来完成此操作。

public class MyMiddleware
{
    private readonly RequestDelegate nextMiddleware;
    private readonly IScriptManager _scriptManager;

    public MyMiddleware(RequestDelegate next, IScriptManager scriptManager)
    {
        this.nextMiddleware = next;
        _scriptManager = scriptManager;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        await nextMiddleware(context);

        var cnt = _scriptManager.ScriptTexts.Count;
        .. get HTML
        Stream originalStream = context.Response.Body;
        ...
        .. update HTML
        await context.Response.WriteAsync(htmlData);
    }
}