What is the correct way to download a file via the NSwag Code Generator (angular 2 typescript)

Question

I try to download a file via an angular 2 typescript client. The link generated in Swagger UI works fine, but the generated typescript client does not.

The controller lo

Answer 1

In the API, Required Nuget packages:

1. Microsoft.AspNetCore.StaticFiles // To determine MimeType
2. NSwag.Annotations // To map the return type of API with Angular Service Generated by NSwag

Search for the pacakges in Nuget and install them.

Then In Startup.cs,

services.AddSwaggerGen(options =>
{
    // Swagger Configurations
    options.MapType(() => new Schema
    {
        Type = "file"
    });
});

Now add a method to get the MimeType of file

private string GetMimeType(string fileName)
{
    var provider = new FileExtensionContentTypeProvider();
    string contentType;
    if (!provider.TryGetContentType(fileName, out contentType))
    {
        contentType = "application/octet-stream";
    }
    return contentType;
} 

Now Add a method to download file

[SwaggerResponse(200, typeof(FileContentResult))]
[ProducesResponseType(typeof(FileContentResult), 200)]
public FileContentResult DownloadDocument(string fileName)
{ 
    // _environment => IHostingEnvironment Instance
    var filepath = Path.Combine($"{this._environment.WebRootPath}\\path-to\\filename}");

    var mimeType = this.GetMimeType(filename);

    // Checks if file exists 
    var fileBytes = File.ReadAllBytes(filepath);
    return new FileContentResult(fileBytes, mimeType)
    {
        FileDownloadName = filename
    };
}

Now the downloadFile method in angular service generated by NSwag will return Observable. To Consume the service, first install file-saver using npm i file-saver. Then import it in component
import { saveAs } from 'file-saver';

downloadDocument = (filename: string): void => {
    this._service.downloadDocument(filename).subscribe((res) => {
      saveAs(res.data, 'filename');
    });
  };

This will download file.