问题
如何在ASP.NET Core 2.0中受限地访问本地目录和文件信息？
答案
新建一个空项目，修改Startup类，添加访问本地文件所需的服务：
public void ConfigureServices(IServiceCollection services){services.AddSingleton<IFileProvider>(new PhysicalFileProvider(Directory.GetCurrentDirectory()));}创建一个中间件，读取根目录下的所有文件，输出文件名：
public class HelloFileProviderMiddleware{private readonly RequestDelegate _next;private readonly IFileProvider _fileProvider;public HelloFileProviderMiddleware(RequestDelegate next, IFileProvider fileProvider){_next = next;_fileProvider = fileProvider;}public async Task Invoke(HttpContext context){var output = new StringBuilder("");IDirectoryContents dir = _fileProvider.GetDirectoryContents("");foreach (IFileInfo item in dir){ ???output.AppendLine(item.Name);}await context.Response.WriteAsync(output.ToString());}}public static class UseHelloFileProviderExtensions{public static IApplicationBuilder UseHelloFileProvider(this IApplicationBuilder app){return app.UseMiddleware<HelloFileProviderMiddleware>();}}运行，此时页面效果：
当然，我们也可以通过IFileProvider接口读取单个文件信息：
public class HelloFileProviderMiddleware{private readonly RequestDelegate _next;private readonly IFileProvider _fileProvider;public HelloFileProviderMiddleware(RequestDelegate next, IFileProvider fileProvider){_next = next;_fileProvider = fileProvider;}public async Task Invoke(HttpContext context){IFileInfo file = _fileProvider.GetFileInfo("Startup.cs");using (var stream = file.CreateReadStream()){ ???using (var reader = new StreamReader(stream)) ???{ ???????var output = await reader.ReadToEndAsync(); ???????await context.Response.WriteAsync(output.ToString()); ???}}}}运行，此时页面效果：
讨论
ASP.NET Core 2.0提供了继承自接口IFileProvider的PhysicalFileProvider类型，用于受限地访问本地文件系统，它是对System.IO.File的一个封装。
我们可以在Startup的Configure()方法内将IFileProvider配置为一个服务，然后通过构造函数注入添加到中间件或者控制器中。这样可以在一个地方控制文件的访问路径（也就是应用程序启动的时候）。
IFileProvider有两个重要的方法：
1. GetDirectoryContents：返回IDirectoryContents接口。可用于遍历某个目录中的全部文件或目录。
2. GetFileInfo：返回IFileInfo接口。通过其CreateReadSteam方法可以读取文件内容。
====start by sanshi=========================
下面通过递归来遍历根目录下全部文件和目录，修改中间件代码：
public class HelloFileProviderMiddleware{private readonly RequestDelegate _next;private readonly IFileProvider _fileProvider;public HelloFileProviderMiddleware(RequestDelegate next, IFileProvider fileProvider){_next = next;_fileProvider = fileProvider;}public async Task Invoke(HttpContext context){var output = new StringBuilder("");ResolveDirectory(output, "", "");await context.Response.WriteAsync(output.ToString());}private void ResolveDirectory(StringBuilder output, string path, string prefix){IDirectoryContents dir = _fileProvider.GetDirectoryContents(path);foreach (IFileInfo item in dir){if (item.IsDirectory){output.AppendLine(prefix + "[" + item.Name + "]");ResolveDirectory(output, item.PhysicalPath.Substring(Directory.GetCurrentDirectory().Length), prefix + " ???");} else{output.AppendLine(prefix + item.Name);}}}} 运行，此时页面效果：
====end by sanshi=========================
源代码下载
原文：https://tahirnaushad.com/2017/08/18/asp-net-core-file-providers/
[译]ASP.NET Core 2.0 本地文件操作
原文地址：http://www.cnblogs.com/sanshi/p/7735941.html