Upload Troubleshooting
The Upload component requires integration with remote endpoints and controller methods to work. Controller routing depends entirely on the app configuration. This article discusses the most common pitfalls.
Action Method Argument null
The action method is hit, but the method argument is null
- Make sure the action method argument names match the
SaveFieldandRemoveFieldvalues. The default value of both parameters is"files". - The argument type of the
SaveUrlaction method should beIFormFileorIEnumerable<IFormFile>. - The argument type of the
RemoveUrlaction method should bestringorIEnumerable<string>. - The uploaded file size may be over the web server's maximum.
HTTP 400 Bad request
The action method is not hit and the server returns HTTP 400 Bad request.
- Make sure that controller routing is enabled and configured correctly. For example, the controller samples in this documentation use
[Route("api/[controller]/[action]")]. It is enough to addapp.MapDefaultControllerRoute();toProgram.csin the default Blazor project template. Web API controllers require explicit[Route]configuration. - Make sure that the
[Route]attribute in the upload controller (if set) is compatible withSaveUrlandRemoveUrl. - Verify that the controller and action method names match the
SaveUrlandRemoveUrlvalues. - Set a
[FromForm]binding source attribute to the action method argument.
HTTP 415 Unsupported Media Type
The Remove action may return HTTP 415 Unsupported Media Type.
This means that the Remove action method expects IEnumerable<string> and .NET does not infer the correct binding source. Set a [FromForm] binding source attribute to the file name argument.
Connection Error and No Response
The server does not return any response. The browser console shows connection errors like:
Failed to load resource: net::ERR_CONNECTION_RESETFailed to load resource: The network connection was lost.
This means that the uploaded file size exceeds the web server's maximum.
Antiforgery Validation Blocks the Upload Requests
If the upload controller is decorated with the [ValidateAntiForgeryToken] attribute, the Upload component must include antiforgery tokens in its upload and delete requests. Use the OnUpload and OnRemove events to add the required antiforgery tokens.