How to allow and manipulate downloads in Cefsharp
By FoxLearn 7/2/2024 8:59:18 AM 215
By default, when embedding a Chromium-based browser in WinForms using the CefSharp library, attempting to download a file from a webpage often results in no visible interaction or progress:
- Clicking a download button or link on a webpage doesn't trigger any download-related action.
- There's no prompt to specify a download location or any indication of a download starting.
- The downloaded file doesn't appear to be saved anywhere, and there's no download progress visible.
This behavior occurs because CefSharp does not handle downloads out-of-the-box without additional configuration and implementation. To manipulate downloads in cefsharp, you need to implement a DownloadHandler
.
public class CustomDownloadHandler : IDownloadHandler { public event EventHandler<DownloadItem> OnBeforeDownloadFired; public event EventHandler<DownloadItem> OnDownloadUpdatedFired; public void OnBeforeDownload(IWebBrowser chromiumWebBrowser, IBrowser browser, DownloadItem downloadItem, IBeforeDownloadCallback callback) { if (downloadItem.IsValid){ // you can get file information } OnBeforeDownloadFired?.Invoke(this, downloadItem); if (!callback.IsDisposed) { using (callback) { callback.Continue( downloadItem.SuggestedFileName, showDialog: true ); } } } public void OnDownloadUpdated(IWebBrowser chromiumWebBrowser, IBrowser browser, DownloadItem downloadItem, IDownloadItemCallback callback) { OnDownloadUpdatedFired?.Invoke(this, downloadItem); if (downloadItem.IsValid) { // Show progress of the download if (downloadItem.IsInProgress && (downloadItem.PercentComplete != 0)) { //"Current Download Speed: {0} bytes ({1}%)", downloadItem.CurrentSpeed, downloadItem.PercentComplete } if (downloadItem.IsComplete) { //The download has been finished } } } }
Initialize CefSharp Browser with Custom DownloadHandler class.
// Initialize cef with the provided settings var settings = new CefSettings(); Cef.Initialize(settings); // Create a browser component var browser = new ChromiumWebBrowser("https://foxlearn.com"); // Register your Custom Downloads Handler browser.DownloadHandler = new CustomDownloadHandler();
Once downloads are allowed and initiated, you might want to manipulate or monitor them:
Use the OnBeforeDownloadFired
event in your CustomDownloadHandler
to get notified before a download starts.
Implement OnDownloadUpdated
in your CustomDownloadHandler
to track progress or handle completion.
You can control the download behavior in OnBeforeDownload
. For instance, you can change the file name, cancel downloads by not calling callback.Continue
, or modify the download directory.
If you want to allow downloads and store them automatically in the downloads directory you can modify your code as shown below.
public class CustomDownloadHandler : IDownloadHandler { public event EventHandler<DownloadItem> OnBeforeDownloadFired; public event EventHandler<DownloadItem> OnDownloadUpdatedFired; public void OnBeforeDownload(IWebBrowser chromiumWebBrowser, IBrowser browser, DownloadItem downloadItem, IBeforeDownloadCallback callback) { // ... OnBeforeDownloadFired?.Invoke(this, downloadItem); if (!callback.IsDisposed) { using (callback) { // Define the Downloads Directory Path string downloadsDirectoryPath = "C:\\Users\\FoxLearn\\Downloads\\"; callback.Continue(Path.Combine(downloadsDirectoryPath, downloadItem.SuggestedFileName), showDialog: false); } } } public void OnDownloadUpdated(IBrowser browser, DownloadItem downloadItem, IDownloadItemCallback callback) { // Handle download progress or completion if needed } }
And that's all you need to do to handle downloads through CefSharp in your project. Once you launch your application and initiate a download from within the embedded Chromium browser, you'll have full control over handling the download process, including specifying where to save the file and monitoring download progress.
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