Reading server-side files using Blazor

Question

I have a project based on the Blazor sample with a .Client, .Server and .Shared projects. I have a textfile data.txt on the server that I want to be able to read/write using standard StreamReader / System.IO.File methods. Since Blazor runs in a sandbox I guess I can't access the entire filesystem as I would in a normal windows app? I've placed the file in the wwwroot directory, and I can even access the file from the client if a enter url/data.txt in the browser so the file gets served, which I don't want to alow, but trying to read that file as such:

var file = File.ReadAllText("data.txt");

Results in the error:

WASM: [System.IO.FileNotFoundException] Could not find file "/data.txt"

How can I read server-side files and keep them hidden from the client?

Answer 1

Turns out this was easier than I thought. I was approaching it from the wrong angle. To access server side files, create a controller as such:

using Microsoft.AspNetCore.Mvc;

namespace Favlist.Server.Controllers
{
    [Route("api/[controller]")]
    public class DataFetcher : Controller
    {
        [HttpGet("[action]")]
        public MyDataClass GetData(string action, string id)
        {
            var str = File.ReadAllText("data.txt");
            return new MyDataClass(str);
        }
    }
}

And call it within your page like so:

@using System.IO;
@page "/dataview"
@inject HttpClient Http

@if (data == null)
{
    <p><em>Loading...</em></p>
}
else
{
    <p>@data.Name</p>
}

@functions {
    MyDataClass data;

    protected override async Task OnInitAsync()
    {
        data = await Http.GetJsonAsync<MyDataClass>("api/DataFetcher/GetData");
    }
}

MyDataClass is your custom class containing whatever you need to read/write.

You can then access files exactly as you normally would, wherever you want on the server. The current directory is your Project.Server root folder.