File uploads with CefSharp

Question

We are using CefSharp (v37.0.0 NuGet package) in a C# WinForms application. We are looking for a way to (programmatically) trigger file upload actions. How, if at all, can that be done? A couple of additional thoughts:

We have a file upload dialog on a page where, normally, a user would select a file. This works fine, we intercept the dialog call via IDialogHandler and provide the file.
Now we want to trigger the same dialog and pre-set the file. While the dialog opens successfully from an "ExecuteScriptAsync" call, we are unable to pre-select the file. Possibly due to the following reason: how to create/initialize the file object using file path html5
Our next idea was to have the dialog open normally and issue a click event programmatically so the browser would open the file dialog (which we would then catch via IDialogHandler and provide the file we desire).
Trying this approach, our observation is as follows:
Following a user action (e.g. button click inside the browser), we can programmatically "click" the file input button.
Doing the same from a call originating via ExecuteScriptAsync, the dialog (or call in IDialogHandler) does not come up.

score 4 · Answer 1 · answered Jan 10 '18 at 20:31

The file TempFileDialogHandler on the CefSharp sample project has an example of this.

    public class TempFileDialogHandler : IDialogHandler
    {
        public bool OnFileDialog(IWebBrowser browserControl, IBrowser browser, CefFileDialogMode mode, string title, string defaultFilePath, List<string> acceptFilters, int selectedAcceptFilter, IFileDialogCallback callback)
        {
            callback.Continue(selectedAcceptFilter, new List<string> { Path.GetRandomFileName() });

            return true;
        }
    }

Replace Path.GetRandomFileName() for your filepath and then attach the handler to the browser like this:

browser.DialogHandler = new TempFileDialogHandler();

score 3 · Accepted Answer · edited May 23 '17 at 12:19

3

Doing the same from a call originating via ExecuteScriptAsync, the dialog (or call in IDialogHandler) does not come up.

This is probably due to the same security restrictions that apply to normal JavaScript: Programmatically open upload file dialog in Chrome

I think you will need to:

In JavaScript:
1. Scroll the file upload button into view, Element.scrollIntoView()
2. Calculate the co-ordinates of the file upload button, Element.getBoundingClientRect()
3. Return the co-ordinates to C#.
In C#:
1. Programmatically send a mouse click to the co-ordinates (see this question)

edited May 23 '17 at 12:19

Community

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answered Dec 29 '14 at 07:05

Yoshi

3,325
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That's definitely an obvious way to do it - thanks for pointing that out Yoshi! We have solved it in a slightly different way now. We let the user click our final "Save" button on the html form. But in this special case we open the "file open" dialog - which works because it originated from a user action -, which we then catch from C# and set the file appropriately. Next, we call the save function again right from the same C# event handler, which will finally run the save/upload logic. Cool stuff this tight interaction between javascript/.NET. – lichtalberich Dec 29 '14 at 07:41

score -2 · Answer 3 · answered Nov 08 '16 at 14:08

-2

I might be wrong but this also can be achieve by using jquery file uploader plugins rather than doing it yourself.

Ajax Upload Uploadify

answered Nov 08 '16 at 14:08

Akshay

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File uploads with CefSharp

3 Answers3