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=========================
总结
以上所述是小编给大家介绍的ASP.NET Core 2.0 本地文件操作问题及解决方案,希望对大家有所帮助,如果大家有任何疑问请给我留言,小编会及时回复大家的。在此也非常感谢大家对脚本之家网站的支持!
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