The upload stream is closing after the loop.

[rodrigo-lemela-duarte]

[EDIT by guardrex to fix the code block ... @rodrigo-lemela-duarte, it's triple-backticks on a line above and below code in a comment]
[EDIT by guardrex to update the report on the var access that results in the error about the closed stream. The error occurs on content access.]

Description

At the FileUpload2.razor code:

This part of the code is throwning error:

var fileContent = new StreamContent(file.OpenReadStream(maxFileSize));

After you get out of the loop and try to access fileContent [should be content, see comment below], .NET throws an error saying that the stream is closed.

The right piece of the code is:

await using var fileStream = uploadedFile.OpenReadStream(maxAllowedSize: maxFileSize);
using var memoryStream = new MemoryStream();
await fileStream.CopyToAsync(memoryStream);
var fileContent = new ByteArrayContent(memoryStream.ToArray());

Page URL

https://learn.microsoft.com/en-us/aspnet/core/blazor/file-uploads?view=aspnetcore-8.0

Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/blazor/file-uploads.md

Document ID

c11d981c-05af-c19d-a333-feedd5978639

Article author

@guardrex

[github-actions]

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[guardrex]

Thanks @rodrigo-lemela-duarte for opening the issue over here. This is the repo where we work issues.

That code, which is part of the FileUpload2 component, isn't supposed to be used that way. The contents of fileContent are only used to establish content for the MultipartFormDataContent, which is used to POST the file content to the server. This scenario is described at the top of the section ...

The following example demonstrates uploading files from a server-side app to a backend web API controller in a separate app, possibly on a separate server.

I think the scenario that you should focus on for a BWA uploading content to the BWA is in the Server-side file upload example section ...

https://learn.microsoft.com/en-us/aspnet/core/blazor/file-uploads?view=aspnetcore-8.0#server-side-file-upload-example

[rodrigo-lemela-duarte]

Hey,

I express my self wrongly and I apoligizy for.
The correct information is:

When you declare that way and use the content (using var content = new MultipartFormDataContent();) on the PostAsync, get the error about the closed stream.
That is the correct statement and the correction is that, in that piece of code.

Why this happen? I don't know, I didn't got deepper on the issue, just look for the correct code and move on.

Thanks.

[guardrex]

I see. Thanks for the clarification.

Let me see if I can reproduce that error here. I'll get back to you soon ... hopefully by tomorrow afternoon.

[guardrex]

I'll leave this open for one of the product unit engineers to take a look during the holidays (or sooner if more bug reports come in), but I can't reproduce a problem with the current demonstration code ...

After changing the generated file extensions to their correct values (.png and .txt) ...

[rodrigo-lemela-duarte]

Strange. Can be something local?
After that change, mentioned on the first comment, my code started to work.

[guardrex]

I don't know ... maybe. The code in the article was approved by the product unit. We'll have to have one of the product unit engineers take a look at this issue.

However, they can't look right now. They're too busy putting the final touches on the .NET 9 release for November.

I'll contact them around the holidays in late November to take a look.

[guardrex]

@rodrigo-lemela-duarte ... Mackinnon just remarked on this (and similar problems). I'll work on adding a section and/or updating the existing approach. See ....

dotnet/aspnetcore#38842