Component upload file

A security best practice for production apps is to avoid sending error messages to clients that might reveal sensitive information about an app, server, or network. Providing detailed error messages can aid a malicious user in devising attacks on an app, server, or network. The example code in this section only sends back an error code number int for display by the component client-side if a server-side error occurs.

If a user requires assistance with a file upload, they provide the error code to support personnel for support ticket resolution without ever knowing the exact cause of the error. For more information on security considerations when uploading files to a server, see Upload files in ASP. The following controller in the Server project saves uploaded files from the client. Because the example uses the app's environment as part of the path where files are saved, additional folders are required if other environments are used in testing and production.

The example saves files without scanning their contents. In the preceding code, GetRandomFileName is called to generate a secure filename. Never trust the filename provided by the browser, as an attacker may choose an existing filename that overwrites an existing file or send a path that attempts to write outside of the app. The following example demonstrates how to upload files in a Blazor Server app with upload progress displayed to the user.

In Blazor Server, file data is streamed over the SignalR connection into. NET code on the server as the file is read. Use the InputFile component to read up to 2 GB of browser file data into.

The maxAllowedSize parameter of OpenReadStream can be used to specify a larger size if required up to a maximum supported size of 2 GB 2,,, bytes.

NET Core 5. In ASP. NET Core 6. NET code on the server as the file is read from the stream. Skip to main content. This browser is no longer supported.

Download Microsoft Edge More info. Contents Exit focus mode. Is this page helpful? Please rate your experience Yes No. Any additional feedback? Warning Always follow security best practices when permitting users to upload files.

Clear ; foreach var file in e. Name, ex. IO using Microsoft. Hosting using Microsoft. Combine Environment. ContentRootPath, Environment. Create ; await file. Feather "trash" icon. Expanded drop zone default : Dragover effect and release capability occurs when a user drags a file or files within at least px of the visible container. Box drop zone : Dragover effect and release capability occurs when a user drags a file or files directly onto the file upload box.

Full-page drop zone : Dragover effect and release capability occurs when a user drags a file or files anywhere on the main area of a page between the header and footer.

Pre-submit errors occur at the time a user attempts to attach a file for things that can be validated at that time e. These errors should prompt a modal describing why the file s couldn't be attached.

For certain types of errors that can only be caught once a user attempts to submit the form e. File upload. Guidelines Dev docs. The file upload component enables users to attach and upload files from their device. Below the hidden file input, we have the file-upload container div, which contains the actual UI that the user will see on the screen.

As an example, we have built this UI with Angular Material components, but of course, the alternative file upload UI could take any form that you like. This UI could be a dialog, a drag and drop zone, or like in the case of our component, just a styled button:. Notice in the component template how the upload blue button and the invisible file input are linked. When the user clicks on the blue button, a click handler triggers the file input via fileUpload.

The user will then choose a file from the file upload dialog, and the change event will be triggered and handled by onFileSelected. Let's now have a look at our component class and the implementation of onFileSelected :. At this point, we would already have a working file upload component. But we want to take this component one step further.

We want to be able to display a progress indicator to the user, and also support upload cancelation. We are going to add a few more elements to the UI of our file upload component. Here is the final version of the file upload component template:.

With this feature, we can get notified of the progress of a file upload via multiple events emitted by the HTTP Observable. To see it in action, let's have a look at the final version of the file upload component class, with all its features implemented:. As we can see, we have set the reportProgress property to true in our HTTP call, and we have also set the observe property to the value events.

Using the events of type UploadProgress , we are saving the ongoing upload percentage in a member variable uploadProgress , which we then use to update the value of the progress indicator bar.

We can make sure that we do so by using the RxJs finalize operator, which is going to call the reset method in both cases: upload success or failure. In our component, we store this subscription object in the uploadSub member variable. While the upload is still in progress, the user might decide to cancel it by clicking on the cancel button.

Then the cancelUpload upload method is going to get triggered and the HTTP request can be canceled by unsubscribing from the uploadSub subscription. In the final version of our file upload component, we can require the user to upload a file of a certain type, by using the requiredFileType property:. This property is then passed directly to the accept property of the file input in the file upload template, forcing the user to select a png file from the file upload dialog.

By default, the browser file selection dialog will allow the user to select only one file for upload. But using the multiple property, we can allow the user to select multiple files instead:. Notice that this would need a completely different UI than the one that we have built. A styled upload button with a progress indicator only works well for the upload of a single file.

For a multi-file upload scenario, there are a variety of UIs that could be built: a floating dialog with the upload progress of all files, etc.