Скачать или смотреть How to Retrieve the FilePath After Completing an Async Download in C# with WebClient

Learn how to effectively get the file path of a downloaded file in C# using the `WebClient` class. This guide simplifies the process with clear steps and code examples.
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This video is based on the question https://stackoverflow.com/q/63402750/ asked by the user 'Andrew Black' ( https://stackoverflow.com/u/13667706/ ) and on the answer https://stackoverflow.com/a/63405047/ provided by the user 'Alexander Petrov' ( https://stackoverflow.com/u/5045688/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding Async Downloads in C#

Downloading files asynchronously can greatly enhance your application's performance, as it allows other processes to continue running during the download. However, you may encounter challenges in tracking the file download status and retrieving the location of the downloaded file. In this post, we'll tackle a common problem that arises when using the WebClient class in C# : How to get the file path after the download has completed.

The Problem

You're using the WebClient class to download a file asynchronously, and while you can initiate the download successfully, you need to know the exact path where the file has been downloaded upon completion. This is crucial for further processing or usage of the downloaded file.

Sample Code for Downloading

Here's a snippet of code that illustrates how you might begin your file download:

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

In this snippet, the DownloadFileAsync method is called with a URI and a path where the file will be saved. After the download is complete, the Wc_DownloadFileCompleted method is invoked.

The Solution

Step 1: Modify the Download Method

To retrieve the file path effectively, you can take advantage of the UserState property in the DownloadFileAsync method. This property allows you to pass additional information into your event handler. Here's how you can implement this:

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

Step 2: Retrieve the File Path in the Completion Handler

Once the download is complete, you can access the UserState property in the completion handler to get the file path. Here’s how to implement that:

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

Key Points to Remember

Always attach the DownloadFileCompleted event handler before starting the download.

Use the UserState parameter in DownloadFileAsync to store the file path, allowing you to access it once the download is finished.

Ensure proper error handling in your event handler to manage any potential issues during the download process.

Conclusion

By following these simple steps, you can successfully retrieve the file path of an asynchronously downloaded file using the WebClient class in C# . This solution not only simplifies your code but also enhances the clarity and usability of your file downloading operations.

If you have any further questions or need additional examples, feel free to reach out in the comments below!