Blazor Server & WebAssembly cannot read large file streams from client

[xPucTu4]

Describe the bug

I want to be able to read files from client browsers using blazor server-side. Using the component, I choose some test file. If the file size is more than 2-3 GB, I cannot read it.
I am not trying to upload the whole file. You can see that from the sample page.

To Reproduce

The clean template with just 1 file added
https://github.com/xPucTu4/BlazorUploadBug

You can create new blazor-server project and just add that file:
https://github.com/xPucTu4/BlazorUploadBug/blob/main/BlazorUploadBug/Pages/Upload.razor

Exceptions (if any)

With file size of about 4GB:
Sometimes JSException with message "[object ProgressEvent]"
With file size of about 3GB there is no exception or any indications of errors.

Further technical details

.NET SDK (reflecting any global.json):
Version: 5.0.100
Commit: 5044b93829

Runtime Environment:
OS Name: Windows
OS Version: 10.0.19041
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\5.0.100\

Host (useful for support):
Version: 5.0.0
Commit: cf258a14b7

.NET SDKs installed:
3.1.302 [C:\Program Files\dotnet\sdk]
5.0.100-rc.2.20479.15 [C:\Program Files\dotnet\sdk]
5.0.100 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.All 2.1.23 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.23 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.0-rc.2.20475.17 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.1.23 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.0-rc.2.20475.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 3.1.9 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.0-rc.2.20475.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

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We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. We will evaluate the request when we are planning the work for the next milestone. To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[Aadael]

Thank you so much - i really thought my brain would explode. I have the same error and as far as I can tell it's the same in Blazor WebAssembly.

[LordBenjamin]

Is the impact of this limited to server-side Blazor?

Currently debugging an issue in Blazor WASM where:

• a 1 GB file works fine
• a file of around 2 GB throws JSException with message [object ProgressEvent]
• a file of around 3.5 GB does not throw exceptions, but calling await stream.ReadAsync(buffer, 0, buffer.Length); always returns 0 (even though the buffer is of non-zero length and stream.Position is 0

I generated a 2 GB test file using:

fsutil file createNew 2gb.txt 2147483647

This might be a separate issue, happy to raise one if it's a different code path to server-side Blazor.

EDIT:

Spent some time on a binary search of working / not working file sizes:

• 2145350000 bytes works as expected
• 2145400000 bytes fails with [object ProgressEvent] exception

So the smallest size that causes a failure must be somewhere in that range.

EDIT 2:

The above was all tested with Chrome.

The 2145400000 byte file that failed in Chrome works in Firefox. Haven't tested further ~2 GB files in FF.

Still able to reproduce the 0-byte reads using the 3.5 GB file in FF.