Can API return a file? #4529

7 Answer(s)

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  0

  drenton created 6 years ago

  Search for "FileDownloadService" in angular project and "FileController" in .Net Core project

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  fguo created 6 years ago

  @drenton Thank you for your clue.

  I found the class of "FileDownloadService" and "FileController", and studied some examples (e.g. getUsersToExcel). It seems to convert a file into a FileDto and return this FileDto as JSON format {"fileName", "fileType", "fileToken"}, but I still couldn't understand how to convert a file content to "fileToken" in server side and how to convert back the FileDto to original file and save it on client side.

  Is there any instruction/tutorial/example about it? Let's say, I have a file example.jpg stored in folder App_Data. How do I build a service on both of Core and Angular sides?

  Thanks,

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  0

  ismcagdas created 6 years ago

  Support Team

  @fguo the file is requested from a Controller at the end of this scenario by the angular client. So, I suggest you to use a controller.

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  fguo created 6 years ago

  Sorry, still don't understand. My need is simple: I have a file "x.jpg" stored in server folder "C:/Files/". How do I code something to let user download it to client side? Can you show me an code example?

  I also need to deal other use-cases about files soon, such as embedding a file (e.g. a picture) into json object, and uploading files into server. I wonder if AspNetZero have built-in functions or easy-to-follow instructions about file handling. If not, it is understandable. I may stop digging it in AspNetZero and try other alternatives for handling files. Can you clarify this?

  Thank you!

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  fguo created 6 years ago

  I figured out my first question, but not 100%. Here is my tests:

  I like to keep as simple as possible at my first test. I created a method in FileController:

  public ActionResult DownloadTestFile()
          {
              var filePath = @"C:\x.xlsx";
              if (!System.IO.File.Exists(filePath))
              {
                  throw new UserFriendlyException(L("RequestedFileDoesNotExists"));
              }
  
              var fileBytes = System.IO.File.ReadAllBytes(filePath);
              return File(fileBytes, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"); 
          }
  

  It works fineas I use a browser and url: <a class="postlink" href="http://localhost:22742/File/DownloadTestFile">http://localhost:22742/File/DownloadTestFile</a>.

  Now, I want to add a fileToken on it. I created a service:

  public class FileAppService : *AppServiceBase, IImageAppService
      {
          private readonly IAppFolders _appFolders;
  
          public FileAppService(IAppFolders appFolders)
          {
              _appFolders = appFolders;
          }
  
          public FileDto GetFile()
          {
              var fileSource = @"C:\x.xlsx";
              var fileName = "example.xlsx";
              var file = new FileDto(fileName, MimeTypeNames.ApplicationVndOpenxmlformatsOfficedocumentSpreadsheetmlSheet);
              var filePath = Path.Combine(_appFolders.TempFileDownloadFolder, file.FileToken);
              if (!Directory.Exists(filePath))
                  Directory.CreateDirectory(filePath);
              File.Copy(fileSource, Path.Combine(filePath, fileName));
  
              return file;
          }
      }
  

  This service works fine. When I test it on swager, it give out a FileDto:

  "result": {
      "fileName": "example.xlsx",
      "fileType": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
      "fileToken": "9a864412394442758089b4256029cd48"
    }
  

  I confirmed It copies the file on C:\aspnet-core\src\SNet.Web.Host\wwwroot\Temp\Downloads\9a864412394442758089b4256029cd48\example.xlsx

  However, when I try to download the file by url: <a class="postlink" href="http://localhost:22742/File/DownloadTempFile?fileType=application/vnd.openxmlformats-officedocument.spreadsheetml.sheet&fileToken=9a864412394442758089b4256029cd48&fileName=example.xlsx">http://localhost:22742/File/DownloadTem ... ample.xlsx</a>,I get exception on code:

  throw new UserFriendlyException(L("RequestedFileDoesNotExists"));
  

  What did I miss? Does the "_appFolders.TempFileDownloadFolder" in FileController point to a different location?

  Thanks,

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  0

  fguo created 6 years ago

  Solved. I wrongly understand the "FileToken". It is used as an encrypted file name, instead of a directory.

  Just change the code:

  if (!Directory.Exists(filePath))
                  Directory.CreateDirectory(filePath);
              File.Copy(fileSource, Path.Combine(filePath, fileName));
  

  as

  File.Copy(fileSource, filePath);
  

  It solved my issue.

  Now, my next questions:

  1. How do I upload files from Angular into server?
  2. Is it possible to embed a file (e.g. a picture) into json object? For example, API returns like { "id": 123, "picture": {/* a jpg file */} }

  Thanks,

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  0

  ismcagdas created 6 years ago

  Support Team

  Hi @fguo,

  Thank you for sharing your solution. You can check demo ui components page for file upload example.

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