Using external JavaScript files in a WinForms/WPF WebBrowser control

Question

I found a cool feature on a website, implemented in JavaScript, I'd like to use it as is in my desktop application (for personal use). During my experiments I managed to generate custom HTML on the fly, feed it to the browser using webBrowser1.DocumentText = [my generated HTML] I've managed to put some inline JavaScript into the HTML, and hook it up via a ScriptManager so that I can call the JavaScript from my C# code, pass a value to it, and get a return value.

But the feature I'm trying to use is a bit more complicated: it's no less than 10 JavaScript files. 2 of them are referenced directly in the web page the usual way <script src="/js/script1.js" type="text/javascript"></script>

The other 8 are loaded in one of the scripts:

var elem = document.createElement("script");
            elem.type = "text/javascript";
            elem.src = "/js/" + filename;
            document.body.appendChild(elem);

These 8 files are in fact data files, even though the data is represented in JavaScript. They're pretty large, over 1MB each. Stuffing it all into the HTML file seems quite stupid. Also, the script that loads the data creates a "file map" and further refers to the data based on which file it's in:

  var fileMap = [
                        [/[\u0020-\u00ff]/, 'file1.js'],
                        [/[\u3000-\u30ff]/, 'file2.js'],
                        [/[\u4e00-\u5dff]/, 'file3.js'],
...

I don't want to resort to modifying the JavaScript, because it's not exactly my strong point. So the browser needs to "see" the js files in order to be able to use them. I thought of creating the file structure locally, and navigating the browser there. But I don't want any loose files in my solution. I'd like to have everything embedded if possible. And I doubt I can get the browser to navigate to an embedded resource, and see other embedded resources as files. Any idea how I could get around this?

EDIT:

I've tried to do it with local files. No luck. I get the HTML to load properly, but when I try to invoke a JavaScript call, nothing happens. I tried pointing the browser to those js files, to make sure they're there. They are. I tried an element with src attribute pointing to an image in the same subfolder as the script files. It gets rendered. It's as if external js files refuse to load.

Answer 1

I had a similar need as your scenario and I addressed it using two key points embedded in two other Stack Overflow answers. As noted by SLaks' answer here the first key is using the syntax file:/// as the prefix for an absolute path to external files. The second is using .Replace("\\\\", "/") for an absolute file path as listed in Adam Plocher's answer and one of his follow-up comments here .

In short, the final output for each external file in an HTML page will look something like:

<link href="file:///c:/users/david/myApp/styles/site.css" rel="stylesheet" type="text/css">

or

<script src="file:///c:/users/david/myApp/scripts/JavaScript1.js"></script>

Using the format in the samples above in my HTML file resulted in the WebBrowser control loading external CSS, image or script files.

The details and solving the scenario in the question

In the womd's answer in the first referenced SO answer above he used the method System.IO.File.ReadAllText() to load script files and embedded the text of the script files into the <head> tag. As you indicated in your question loading script files directly into the HTML page is not what you're looking to do.

The solution below involves using the same System.IO.File.ReadAllText() method but loads the text of the HTML page instead. The premise works similar to the Razor View Engine in ASP.NET.

The main idea in the solution below involves adding a temporary string in an HTML page that will be loaded into the WebBrowser control and then replacing this temporary string in a C# method in my app just before the HTML page is set to be loaded into the WebBrowser control.

Here are the basic steps to my solution:

Add a temporary string for each external reference in the HTML file.
Declare a variable for the absolute path in a script tag within the HTML file. This step is not necessary unless you're going to use the absolute path elsewhere within your JavaScript code. Your scenario involves delay loading external script files via JavaScript code so this step was necessary.
Modify the src property in the JavaScript code that delay loads the other script files with the absolute path variable.
Add a method in your app to loads the HTML page file as a text string and then replaces all temporary string instances with an absolute path containing the prefix 'file:///'. The absolute path should have forward slashes.
Set the 'DocumentText' property on the WebBrowser control to the updated HTML.
Set the 'Copy to Output Directory' of each external file in your project to 'Copy always' or 'Copy if newer'. This step may not be necessary if you have a fixed location to your external files and that location is not within the build or publish directory used by Visual Studio.

The following are the details for each step. I added a lot of detail that you can skip. I was verbose to reduce any confusion since the steps make changes to several places in the project.

1. Using a temporary string

I used the string "/ReplaceWithAbsolutePath/" but you can use any distinct text. Each reference to an external file in the HTML page looks like:

<!DOCTYPE html>
<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="utf-8" />
    <title></title>
    <link href="/ReplaceWithAbsolutePath/styles/site.css" rel="stylesheet" type="text/css">
    <script type="text/javascript">
        var absolutePath = "/ReplaceWithAbsolutePath/";
    </script>
</head>
<body>
    <p>My web page</p>
    <script src="/ReplaceWithAbsolutePath/scripts/JavaScript1.js"></script>
</body>
</html>

2. Declare absolute path variable

Note in the above HTML page I listed a <script> tag with the declared variable 'absolutePath' set to the temporary string. (In the HTML page above the variable is added a global variable and that is not necessarily best practice. You can declare the variable within a namespace instead of declaring it in the global namespace.)

3. Modify the delay load script to include absolute path variable

Add the 'absolutePath' variable to your JavaScript file that delay loads other JavaScript files containing your data.

elem.src = absolutePath + "/js/" + filename;

4. C# method to replace all temporary string instances

Within your project add the following line to your form load event handler or place this line somewhere in your initialization of the WebBrowser control.

webBrowser1.DocumentText = GetUpdatedHtmlWithAbsolutePaths("/ReplaceWithAbsolutePath/", "HTMLPage1.html");

Add the following method to your code. Update the call to the method in the line above with the name of the class instance where the following method is placed.

    // The result of this method will look like the following example:
    // <script src="file:///c:/users/david/documents/myApp/scripts/JavaScript1.js"></script>
    public string GetUpdatedHtmlWithAbsolutePaths(string tempPathString, string htmlFilename)
    {
        // Get the directory as the application
        // stackoverflow.com/questions/674857/should-i-use-appdomain-currentdomain-basedirectory-or-system-environment-current
        // Note that the 'BaseDirectory' property will return a string with trailing backslashes ('\\')
        string appDirectory = AppDomain.CurrentDomain.BaseDirectory;
        // Replace '//' with '/' in the appDirectory string
        appDirectory = appDirectory.Replace("\\", "/");
        // Read all of the HTML text from the HTML page file
        string html = System.IO.File.ReadAllText(appDirectory + @"\" + htmlFilename);
        // Replace all '/ReplaceWithAbsolutePath/' strings within the HTML text with
        // the absolute path on the local machine
        html = html.Replace(tempPathString, "file:///" + appDirectory);
        return html;
    }

5. Set the DocumentText property of the WebBrowser control

I added the initialization of the WebBrowser control in the form load event handler but you can, of course, add the line that sets the DocumentText property wherever you initialize your WebBrowser control.

    private void Form1_Load(object sender, EventArgs e)
    {
        // Set the document text of the web browser control with the updated HTML
        webBrowser1.DocumentText = GetUpdatedHtmlWithAbsolutePaths("HTMLPage1.html");
    }

6. Set the 'Copy to Output Directory' of each external file

Take a look at the answer posted by Matthew Watson in this Stack Overflow question if you want your external files included in your solution/project file structure.

You can add files to your project and select their properties: "Build Action" as "Content" and "Copy to output directory" as "Copy Always" or Copy if Newer (the latter is preferable because otherwise the project rebuilds fully every time you build it).

Then those files will be copied to your output folder.

This is better than using a post build step because Visual Studio will know that the files are part of the project. (That affects things like ClickOnce applications which need to know what files to add to the clickonce data.)

In short, add the external file to your project. You can add the external to any subfolder in your project. (In Visual Studio 2013 or 2015 -- I don't have VS2012) Right-click on the external file in the Solution Explorer and select Properties from the context menu. The Properties pane will be displayed. In the Properties pane change the setting for 'Copy to Output Directory' to 'Copy always' or 'Copy if newer'.

Use View Source to verify absolute path strings

Run your project and it should load your external files in the WebBrowser control. Assuming you have not set the property wbChartContainer.IsWebBrowserContextMenuEnabled = false; in code or in the Properties pane for WebBrowser control you can right-click on the WebBrowser control when your form is running. Click 'View Source' from the context menu and check the paths to your external resources in the View Source window.

Using external JavaScript files in a WinForms/WPF WebBrowser control

Question

1 answers

solution1
0 2015-12-16 20:40:36

The details and solving the scenario in the question

1. Using a temporary string

2. Declare absolute path variable

3. Modify the delay load script to include absolute path variable

4. C# method to replace all temporary string instances

5. Set the DocumentText property of the WebBrowser control

6. Set the 'Copy to Output Directory' of each external file

Use View Source to verify absolute path strings

Using external JavaScript files in a WinForms/WPF WebBrowser control

Question

1 answers

solution1 0 2015-12-16 20:40:36

The details and solving the scenario in the question

1. Using a temporary string

2. Declare absolute path variable

3. Modify the delay load script to include absolute path variable

4. C# method to replace all temporary string instances

5. Set the DocumentText property of the WebBrowser control

6. Set the 'Copy to Output Directory' of each external file

Use View Source to verify absolute path strings

solution1
0 2015-12-16 20:40:36