Image upload in .NET Core Web API

Question

I'm developing a Web API with .Net Core, where I need to allow a client to upload a list of files (mostly images) and save them to the server.

Im using ASP.NET Core 3.0

This is my startup file Startup.cs:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.AspNetCore.Http;


namespace ImageUplaodDemo
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}

This is my ImageController file ImageController.cs:

using System;
using System.IO;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
namespace ImageUploadDemo.Controllers
{
    [Route("api/[controller]")]
    public class ImageController : ControllerBase
    {
        public static IHostingEnvironment _environment;
        public ImageController(IHostingEnvironment environment)
        {
            _environment = environment;
        }
        public class FIleUploadAPI
        {
            public IFormFile files { get; set; }
        }
        [HttpPost]
        public async Task<string> Post(FIleUploadAPI files)
        {
            if (files.files.Length > 0)
            {
                try
                {
                    if (!Directory.Exists(_environment.WebRootPath + "\\uploads\\"))
                    {
                        Directory.CreateDirectory(_environment.WebRootPath + "\\uploads\\");
                    }
                    using (FileStream filestream = System.IO.File.Create(_environment.WebRootPath + "\\uploads\\" + files.files.FileName))
                    {
                        files.files.CopyTo(filestream);
                        filestream.Flush();
                        return "\\uploads\\" + files.files.FileName;
                    }
                }
                catch (Exception ex)
                {
                    return ex.ToString();
                }
            }
            else
            {
                return "Unsuccessful";
            }
        }
    }
}

Im trying to upload a image using POSTMAN by POST operation. I assigned REQUEST to POST and im using form-data under Body tag and assigned KEY as file to upload a file from the desktop. But im getting the following error.

I have tried all possible but been getting the same error...

Check through the code once and there any modification need to be done on the code or any modifications on postman....

{
    "type": "https://tools.ietf.org/html/rfc7231#section-6.5.13",
    "title": "Unsupported Media Type",
    "status": 415,
    "detail": null,
    "instance": null,
    "extensions": {
        "traceId": "|2c45b532-43521b159e7b734f."
    }
}

Answer 1

[HttpPost("UploadFile")]
 public async Task<string> UploadFile([FromForm] IFormFile file)
    {
        string fName = file.FileName;
        string path = Path.Combine(hostingEnvironment.ContentRootPath, "Images/" + file.FileName);
        using (var stream = new FileStream(path, FileMode.Create))
        {
            await file.CopyToAsync(stream);
        }
        return file.FileName; 
    }

You can use this in your controller class. Don't need to create a FileUploadAPi class.

Answer 2

Remove these lines:

app.Run(async (context) =>
{
    await context.Response.WriteAsync("Controller didn't find anything!");
});

You're short-circuiting every request and just returning "Controller didn't find anything!" with that. Nothing ever even makes it into the pipeline.

Answer 3

Hey have you tried the official docus?

https://learn.microsoft.com/en-us/aspnet/core/mvc/models/file-uploads?view=aspnetcore-2.2

and this one https://learn.microsoft.com/en-us/aspnet/core/tutorials/first-web-api?view=aspnetcore-2.2&tabs=visual-studio

I would try to use official sources to learn topics like this, instead of random blogs.

Have you debugged your controller? Is the IFormFile in your viewmodel already mapped?

The controller should be found automatically and respond to:

http(s)://localhost:DEVPORT/api/Image

You could add an Index Endpoint returning a string "Hello World" and you should see a Json Response , when you try to connect with your browser..

Not sure why you are doing this:

app.Run(async (context) =>
            {
                await context.Response.WriteAsync("Controller didn't find anything!");
            });

Did you send the right body in your post request?