Скачать или смотреть Solving .NET 7 System.IO.FileNotFoundException: Could Not Find File in Blazor WebAssembly Projects

Discover how to resolve the `.NET 7 System.IO.FileNotFoundException` issue in your Blazor WebAssembly project effectively and prevent file upload failures.
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This video is based on the question https://stackoverflow.com/q/74639679/ asked by the user 'jcadafalch' ( https://stackoverflow.com/u/20634897/ ) and on the answer https://stackoverflow.com/a/74640311/ provided by the user 'StefanFFM' ( https://stackoverflow.com/u/5629588/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving .NET 7 System.IO.FileNotFoundException in Blazor WebAssembly Projects

When working with file uploads in a Blazor WebAssembly application, you might encounter an error that reads System.IO.FileNotFoundException: Could not find file. This issue can be frustrating and hinder your development process, especially if you're new to Blazor or the .NET framework. In this guide, we will dissect this problem and provide a clear solution to help you successfully upload files without running into this error.

The Problem

In many scenarios where files are uploaded, a common reliance is placed on the file's physical existence on the server's file system. However, in Blazor WebAssembly applications, the files that are uploaded by users are not stored on the server's file system. Instead, they exist in-memory. This can lead to confusion when trying to access these files after they have been uploaded, which is likely the reason behind the FileNotFoundException you are seeing.

Your code looks something like this:

[[See Video to Reveal this Text or Code Snippet]]

When you attempt to read the file using File.ReadAllBytes(destPath + file.Name);, the application can't find the file, leading to the exception.

The Solution

To fix this issue, you need to access the uploaded file data directly from the IBrowserFile interface instead of trying to read it from a non-existent file path. Here's a detailed explanation of how to do this:

Step 1: Open the Uploaded File

Instead of using the File.ReadAllBytes method, leverage the OpenReadStream method from the IBrowserFile interface. This allows you to work with the file in memory.

Step 2: Read File Data into Memory

You will want to copy the contents of the uploaded file to a memory stream. Here's how you can modify your upload method:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Handle User Notifications

If some files fail to upload, you can inform the users using the Snackbar component as illustrated in your original code. This keeps users informed about the process and any issues.

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Encountering a System.IO.FileNotFoundException is a common hurdle when developing Blazor WebAssembly applications, especially for those new to the framework. By recognizing that uploaded files are stored in-memory rather than on the file system, you can adjust your approach to file handling accordingly. Follow these outlined steps, and you'll be able to process file uploads effectively without running into file not found errors.

Happy coding, and may all your file uploads be successful!