Blazor Server-Side download issues in IIS

Question

I am trying to download a List of files (user has the option to select multiple). My current code below works fine in localhost (writing and opening the downloads folder). However, when I upload to IIS it gives an error saying that the system configuration is not found. Please see below:

if (SelectDownloadFiles.Count > 0)
{
    //Downloads folder (User profile)
    string DownloadFolder = Environment.ExpandEnvironmentVariables("%userprofile%/downloads/");

    //This is a little hack to get the literal path for the Downloads folder without too much of back-and-forth and ellaboration
    string FolderForward = DownloadFolder.Replace(@"/", @"\");
    string Folder = FolderForward.Replace(@"\\", @"\");

    foreach (var items in SelectDownloadFiles)
    {
        //Get Date
        var GetDate = items.Substring(0, 6);

        //Add 2 days to be consistent to what is displayed to the user (when files were generated)
        var FileDate = DateTime.ParseExact(GetDate, "yyMMdd", CultureInfo.InvariantCulture).AddDays(2);

        //Get Files
        string Pathname = @"D:\";
        string FullPathName = Path.Combine(Pathname, items);
        byte[] FileBytes = System.IO.File.ReadAllBytes(FullPathName);
        MemoryStream Ms = new MemoryStream(FileBytes);

        //Rename the file to become user friendly
        string DownloadPath = Path.Combine(DownloadFolder, "My Files " + FileDate.ToString("MM-dd-yyyy") + ".zip");

        //Write file(s) to folder
        FileStream File = new FileStream(DownloadPath, FileMode.Create, FileAccess.Write);
        Ms.WriteTo(File);
        File.Close();
        Ms.Close();
    }

    //Open Downloads Folder with files
    Process.Start("explorer.exe", Folder);
    navigationManager.NavigateTo("/default", true);

    //DisplayMessage.Show("File(s) successfully downloaded. Please check your “Downloads” folder to access your file(s).", "OK", "check");
}
else
{
    Toaster.Add("Please select at least one file to download.", MatToastType.Warning);
}

I've also tried to use the solution below to no avail:

 private readonly IWebHostEnvironment _webHostEnvironment;

    public YourController (IWebHostEnvironment webHostEnvironment)
    {
        _webHostEnvironment= webHostEnvironment;
    }

If I use the "folderoptionpath" and choose "MyDocuments" for instance, the files download to the root path of the files inside IIS. Is there anything else I need to be doing to get to this to work? Thanks in advance!

To let your web application create files locally on the server, you have to take care of permissions. One way is to create a "temp" directory (not in the wwwroot) and to add read-write rights on this folder for the IIS_IURS user (or other user defined in your application pool). Then change your code to upload file in this directory. — , Jun 14 '21 at 16:23
@GuyatMercator, what about writing to User's download folder? Is that an option? — 1moreLearner, Jun 14 '21 at 17:52
The problem is that this code isn't "downloading" anything at all. It simply writes to the filesystem it the machine where it's executing. That's fine when you're testing locally and client and server happen to be the same device. As you've discovered, it comes unstuck when you move the server to a separate machine. What you actually need to do in a normal web app is prepare a http response containing the file data and the appropriate http headers, so the browser sees it as a download rather than a page. In blazor, I confess I'm not so sure of the best way, but certainly not your current way. — ADyson, Jun 14 '21 at 18:04
P.s. https://stackoverflow.com/questions/52683706/how-can-one-generate-and-save-a-file-client-side-using-blazor could be what you need — ADyson, Jun 14 '21 at 18:11

score 1 · Accepted Answer · answered Jun 16 '21 at 19:48

Well, after spending some time researching this, I was finally able to get it going. I ended up using a Nuget Package called BlazorFileSaver and it works just fine. Here's the repo: https://github.com/IvanJosipovic/BlazorFileSaver/blob/master/src/BlazorFileSaver.Sample/Pages/Index.razor I hope this can help someone else in the future.

Blazor Server-Side download issues in IIS

1 Answers1