How to handle Javascript events via WebBrowser control for WinForms - javascript

I have read WebBrowser Control from .Net — How to Inject Javascript, Is it possible to call Javascript method from C# winforms and many others. Those examples were returns function value or alert window (synchronous calls). I have to get result from event handler (async call):
<script type="text/javascript">
window.onload = function() {
var o = new M.Build(document.getElementById("ZID"));
M.Events.observe(o, o.Events.Success, function() {
// I have to get some value!!
});
M.Events.observe(o, o.Events.Fault, function() {
// I have to get some value!!
});
}
</script>

Calling C# from JavaScript
Simply put, you can expose a C# object
to the WebBrowser that the JavaScript
can call directly The WebBrowser
class exposes a property called
ObjectForScripting that can be set by
your application and becomes the
window.external object within
JavaScript. The object must have the
ComVisibleAttribute set true
C#:
[System.Runtime.InteropServices.ComVisibleAttribute(true)]
public class ScriptInterface
{
public void callMe()
{
… // Do something interesting
}
}
webBrowser1.ObjectForScripting = new ScriptInterface();
Javascript:
window.external.callMe();
Calling JavaScript in a WebBrowser control from C#

This is code I have. In the DocumentCompleted event ('cause I'm getting a page from online)
var wb = (WebBrowser)sender
//Lots of other stuff
object obj = wb.Document.InvokeScript("MyFunctionName");
Create a function that returns whatever value you need and invoke away.
You can also inject a script into the page
string js = "function MyFunctionName(){alert('Yea!');}";
HtmlElement el = wb.Document.CreateElement("script");
IHTMLScriptElement element2 = (IHTMLScriptElement)el.DomElement;
element2.text = js;
head.AppendChild(el);
which can then be invoked. That's what I've done.

If your webBrowser control is in a form, you can do the following:
[System.Runtime.InteropServices.ComVisibleAttribute(true)]
public class Form1
{
public Form1()
{
InitializeComponent();
webBrowser1.ObjectForScripting = this;
}
public void CallMe()
{
//.... this method can be called in javascript via window.external.CallMe();
}
}

Related

C# winforms webbrowser control with Javascript

I have an HTML page loaded in the webbrowser control. The HTML has a javascript function windows.print which tries to print from my browser. Please how can I pass the windows.print() function to print through Winforms C#. Or how can I pass the javascript object I want printed into the C# to be printed.
Please I am a beginner with C#, I would appreciate a detailed explanation. Thanks so much!
you can probably do something like this
namespace WindowsFormsApplication
{
// This first namespace is required for the ComVisible attribute used on the ScriptManager class.
using System.Runtime.InteropServices;
using System.Windows.Forms;
// This is your form.
public partial class Form1 : Form
{
// This nested class must be ComVisible for the JavaScript to be able to call it.
[ComVisible(true)]
public class ScriptManager
{
// Variable to store the form of type Form1.
private Form1 mForm;
// Constructor.
public ScriptManager(Form1 form)
{
// Save the form so it can be referenced later.
mForm = form;
}
// This method can be called from JavaScript.
public void MethodToCallFromScript()
{
// Call a method on the form.
mForm.DoSomething();
}
// This method can also be called from JavaScript.
public void AnotherMethod(string message)
{
MessageBox.Show(message);
}
}
// This method will be called by the other method (MethodToCallFromScript) that gets called by JavaScript.
public void DoSomething()
{
// Indicate success.
MessageBox.Show("It worked!");
}
// Constructor.
public Form1()
{
// Boilerplate code.
InitializeComponent();
// Set the WebBrowser to use an instance of the ScriptManager to handle method calls to C#.
webBrowser1.ObjectForScripting = new ScriptManager(this);
// Create the webpage.
webBrowser1.DocumentText = #"<html>
<head>
<title>Test</title>
</head>
<body>
<input type=""button"" value=""Go!"" onclick=""window.external.MethodToCallFromScript();"" />
<br />
<input type=""button"" value=""Go Again!"" onclick=""window.external.AnotherMethod('Hello');"" />
</body>
</html>";
}
}
}

Understanding Android webview javascript interface

I have created an android WebView, and injected javascript interface using addJavascriptInterface(mObject, "jsinterface"). It works fine until I create an object with same name (jsinterface) in JavaScript using the new operator.
My Java Code:
WebView mWebView = findViewById(R.id.myWebView);
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.setWebChromeClient(new MyWebChromeClient((Activity)mContext));
mWebView.addJavascriptInterface(new testClass(), "jsinterface");
mWebView.loadUrl("UrlToLoad");
testClass.java
public class testClass{
public testClass() {
}
#JavascriptInterface
public String testNativeMethod() {
return "Java method called!!";
}
}
My Java Script Code
test.js
function test(msg){
this.message = msg;
this.testJSMethod = function(){
return this.message;
}
}
alert(jsinterface.testNativeMethod()); // prints Java method called!!
jsinterface= new test("JS method called...");
alert(jsinterface.testJSMethod()); // prints JS method called...
alert(jsinterface.testNativeMethod()); // errors "NPMethod called on non- NPObject"
Problem:
Is this possible for a javascript object to have access to both , i.e javascript methods and native JAVA methods(exposed to it via javascriptinterface) ? Is there any possibility of setting any property to webview OR executing any JS script to get this done?
Think about document in javascript. When you are in a web browser, this is a global object that you have access to at any point. If you make your own new var called document, you are going to have problems accessing the global document.
When you execute this line:
mWebView.addJavascriptInterface(new testClass(), "jsinterface");
you are adding a global object called jsinterface. This is the same situation as document. If you create a var with the same name, it will overwrite the existing global reference.
Once you add a javascript interface to the WebView, you don't need to create a new reference to the interface. addJavascriptInterface has already done that for you.
TRY
You may try to make another object, which will retranslate calls to javascript interface.Implement onPageStarted method in WebViewClient , and inject javascript in onPageStarted method, in the following way.
mWebView.setWebViewClient(new WebViewClient() {
#Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
view.loadUrl(url);
return true;
}
#Override
public void onPageStarted (WebView view, String url, Bitmap favicon){
String jsScript= "javascript:var functions_array = ['testNativeMethod'];";
jsScript+="var jsinterface = {};"
jsScript+="functions_array.map(function(id){"
jsScript+="jsinterface[id]= function() {"
jsScript+="try{return temp_obj[id].apply(temp_obj, arguments);}"
jsScript+="catch(e) { console.log('ERROR: ' + e + ', method ' + id);"
jsScript+="return false;}}})"
view.loadUrl(jsScript);
}
});
Hope this helps :-)

Is it possible to wait for answer from window.external.Foo() call?

I am using a JavaScript within a .Net Wrapper(WebBrowser control)
I would like to run a .Net Function and wait for it to return a value for the JavaScript,
I am able to call the function from the JS but wasnt able to wait for it to return a value,
for example, my JS code is:
IsConnected = function()
{
var answer = window.external.IsConnected();
};
My C# code is:
[ComVisible(true)]
public class JavaScriptBackEnd
{
public bool IsConnected()
{
if (verifyConnection())
{
return true;
}
return false;
}
}
Is there a way within either C# or JavaScript for me to block the JS function until the "IsConnected" function finishes and returns a value?
Thanks!
Be sure to include the following when setting up your Web browser control (assuming webBrowser is the name of your control) :
webBrowser.ObjectForScripting = new JavaScriptBackEnd(this);
This tells the Web browser where to look for the scripts.

How to connect a C# ActiveX event handler in Javascript

Utilizing several code snippets I've attempted to hook up an ActiveX object with a Javascript event handler. I'm unable to identify why the event handler isn't being called.
Github Repository with project.
Update
By placing the javascript call to SayHello() in an 'onLoad' event, I was able to get the ActiveX event to fire. Now I'm looking toward the C# call, and how to hook it into the ActiveX object utilized by Javascript.
(This may also have relied on enable local scripts from the Advanced options of IE).
Message Continued
The event handler is done in the same form as described for this question.
<script for="MyObject" event="OnUpdateString(stuff)">
document.write("<p>" + stuff);
document.writeln("</p>");
</script>
Utilizing MSDN documentation I created a WinForms app that contains a WebBrowser control that acts as the ObjectForScripting (not related to the issue). This container makes a call out to the ActiveX event, but is unhandled by the Javascript. I'm including the C# Form code to be complete in the ActiveX interactions and to allow this to be a reference for future users of ActiveX and/or WebBrowser control.
This file is intended to be used with a new Windows Form project where a WebBrowser control was added to the main window.
C# Form1.cs
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Security.Permissions;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using ActiveXObjectSpace;
namespace TestActiveX
{
[PermissionSet(SecurityAction.Demand, Name = "FullTrust")]
[System.Runtime.InteropServices.ComVisibleAttribute(true)]
public partial class Form1 : Form
{
MyObject myObject = new MyObject();
public Form1()
{
InitializeComponent();
Text = "ActiveX Test";
Load += new EventHandler(Form1_Load);
}
private void Form1_Load(object sender, EventArgs e)
{
webBrowser1.AllowWebBrowserDrop = false;
webBrowser1.ObjectForScripting = this;
webBrowser1.Url = new Uri(#"C:\path\to\TestPage.html");
// Call ActiveX
myObject.SayHello("C# Launch");
}
public string ControlObject()
{
return "<p>Control Object Called.</p>";
}
}
}
Combining from the help of two other code snippets I created a the ActiveX object. Which, as noted, needs to be registered after being built.
C# ObjectX.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.InteropServices;
/// http://blogs.msdn.com/b/asiatech/archive/2011/12/05/how-to-develop-and-deploy-activex-control-in-c.aspx
/// https://stackoverflow.com/questions/11175145/create-com-activexobject-in-c-use-from-jscript-with-simple-event
///
/// Register with %NET64%\regasm /codebase <full path of dll file>
/// Unregister with %NET64%\regasm /u <full path of dll file>
namespace ActiveXObjectSpace
{
/// <summary>
/// Provides the ActiveX event listeners for Javascript.
/// </summary>
[Guid("4E250775-61A1-40B1-A57B-C7BBAA25F194"), InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
public interface IActiveXEvents
{
[DispId(1)]
void OnUpdateString(string data);
}
/// <summary>
/// Provides properties accessible from Javascript.
/// </summary>
[Guid("AAD0731A-E84A-48D7-B5F8-56FF1B7A61D3"), InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
public interface IActiveX
{
[DispId(10)]
string CustomProperty { get; set; }
}
[ProgId("MyObject")]
[ComVisible(true)]
[ClassInterface(ClassInterfaceType.AutoDual)]
[Guid("7A5D58C7-1C27-4DFF-8C8F-F5876FF94C64")]
[ComSourceInterfaces(typeof(IActiveXEvents))]
public class MyObject : IActiveX
{
public delegate void OnContextChangeHandler(string data);
new public event OnContextChangeHandler OnUpdateString;
// Dummy Method to use when firing the event
private void MyActiveX_nMouseClick(string index)
{
}
public MyObject()
{
// Bind event
this.OnUpdateString = new OnContextChangeHandler(this.MyActiveX_nMouseClick);
}
[ComVisible(true)]
public string CustomProperty { get; set; }
[ComVisible(true)]
public void SayHello(string who)
{
OnUpdateString("Calling Callback: " + who);
}
}
}
Last is the html page which is to be loaded by the browser or container. It loads the ActiveX object successfully and contains an event handler for OnUpdateString. It checks that the ActiveX provided function, SayHello, can be called and makes the call.
I'd expect the Javascript and C# call to be written to the document, but no such entries are written.
TestPage.html
<!DOCTYPE html>
<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>DemoCSharpActiveX webpage</title>
</head>
<body>
<script type="text/javascript">
window.objectLoadFailure = false;
</script>
<object id="MyObject" onerror="window.objectLoadFailure = true" classid="clsid:7A5D58C7-1C27-4DFF-8C8F-F5876FF94C64"></object>
<script for="MyObject" event="OnUpdateString(stuff)">
document.write("<p>" + stuff);
document.writeln("</p>");
</script>
<script type="text/javascript">
document.write("<p>Loaded ActiveX Object: " + !window.objectLoadFailure);
document.writeln("</p>");
if (typeof window.external.ControlObject !== "undefined") {
document.write(window.external.ControlObject());
}
var obj = document.MyObject;
if (typeof obj.SayHello !== "undefined") {
document.writeln("<p>Can Call say hello</p>")
}
obj.SayHello("Javascript Load");
</script>
</body>
</html>
The containing page shows this output
Output
Loaded ActiveX Object: true
Control Object Called.
Can Call say hello
Updated, as long as you can get the <object> instantiated from HTML (MyObject.object != null), the ultimate problem with your JavaScript event handler is simply that you kill the original HTML document with document.write before you call MyObject.SayHello("Javascript Load"), and replace it with <p>Loaded ActiveX Object: ...</p>. By then, all original JavaScript event handlers are gone.
Thus, the following works fine, the event gets fired and handled (with an alert):
<!DOCTYPE html>
<html>
<head>
<title>DemoCSharpActiveX webpage</title>
</head>
<body>
<script type="text/javascript">
window.objectLoadFailure = false;
</script>
<object id="MyObject" onerror="window.objectLoadFailure = true" classid="clsid:7A5D58C7-1C27-4DFF-8C8F-F5876FF94C64"></object>
<script type="text/javascript" for="MyObject" event="OnUpdateString">
alert("Hello from event handler");
</script>
<script type="text/javascript" for="window" event="onload">
alert("Hello from window.onload!");
alert(MyObject.object);
MyObject.SayHello("Javascript Load");
</script>
</body>
</html>
To make your original logic work, you can manipulate the DOM directly instead of using document.write. Or, at least call it after OnUpdateString has been fired and handled.
Now that I've seen the full source, I can tell quite a few things going wrong here.
You can hit a break point inside SayHello because you create MyObject from C# [MyObject myObject = new MyObject()] and call it from C# [myObject.SayHello("C# Launch")]. Remove that and you'll see it never gets invoked when you call it from JavaScript [obj.SayHello("Javascript Load")].
That leads to another issue: the <object> doesn't get create successfully, and even more so, none of your JavaScript scripts even run, because your test HTML file is served from the local file system (via file:// protocol). This is a security restriction. Try changing your script like below to see none of the alerts actually show up:
<script type="text/javascript" for="window" event="onload">
alert("Hello from window.onload!");
alert(MyObject.object) // null! object wasn't created...
document.write("<p>Loaded ActiveX Object: " + !window.objectLoadFailure);
document.writeln("</p>");
if (typeof window.external.ControlObject !== "undefined") {
document.write(window.external.ControlObject());
}
var obj = document.MyObject;
if (typeof obj.SayHello !== "undefined") {
document.writeln("<p>Can Call say hello</p>")
}
obj.SayHello("Javascript Load");
</script>
There're several ways of fixing it. The easiest one is probably to use "Mark of Web". The hardest one would be to provide a custom implementation of IInternetSecurityManager. I myself would use yet another method - Internet Feature Control - and disable FEATURE_LOCALMACHINE_LOCKDOWN, FEATURE_BLOCK_LMZ_SCRIPT, FEATURE_BLOCK_LMZ_OBJECT keys. You can use following code I adapted from my other related answer:
// static constructor, runs first
static Form1()
{
SetWebBrowserFeatures();
}
static void SetWebBrowserFeatures()
{
// don't change the registry if running in-proc inside Visual Studio
if (LicenseManager.UsageMode != LicenseUsageMode.Runtime)
return;
var appName = System.IO.Path.GetFileName(System.Diagnostics.Process.GetCurrentProcess().MainModule.FileName);
var featureControlRegKey = #"HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main\FeatureControl\";
Registry.SetValue(featureControlRegKey + "FEATURE_BROWSER_EMULATION",
appName, GetBrowserEmulationMode(), RegistryValueKind.DWord);
// enable the features which are "On" for the full Internet Explorer browser
Registry.SetValue(featureControlRegKey + "FEATURE_ENABLE_CLIPCHILDREN_OPTIMIZATION",
appName, 1, RegistryValueKind.DWord);
Registry.SetValue(featureControlRegKey + "FEATURE_AJAX_CONNECTIONEVENTS",
appName, 1, RegistryValueKind.DWord);
Registry.SetValue(featureControlRegKey + "FEATURE_GPU_RENDERING",
appName, 1, RegistryValueKind.DWord);
Registry.SetValue(featureControlRegKey + "FEATURE_WEBOC_DOCUMENT_ZOOM",
appName, 1, RegistryValueKind.DWord);
Registry.SetValue(featureControlRegKey + "FEATURE_NINPUT_LEGACYMODE",
appName, 0, RegistryValueKind.DWord);
Registry.SetValue(featureControlRegKey + "FEATURE_LOCALMACHINE_LOCKDOWN",
appName, 0, RegistryValueKind.DWord);
Registry.SetValue(featureControlRegKey + "FEATURE_BLOCK_LMZ_SCRIPT",
appName, 0, RegistryValueKind.DWord);
Registry.SetValue(featureControlRegKey + "FEATURE_BLOCK_LMZ_OBJECT",
appName, 0, RegistryValueKind.DWord);
}
static UInt32 GetBrowserEmulationMode()
{
int browserVersion = 0;
using (var ieKey = Registry.LocalMachine.OpenSubKey(#"SOFTWARE\Microsoft\Internet Explorer",
RegistryKeyPermissionCheck.ReadSubTree,
System.Security.AccessControl.RegistryRights.QueryValues))
{
var version = ieKey.GetValue("svcVersion");
if (null == version)
{
version = ieKey.GetValue("Version");
if (null == version)
throw new ApplicationException("Microsoft Internet Explorer is required!");
}
int.TryParse(version.ToString().Split('.')[0], out browserVersion);
}
if (browserVersion < 7)
{
throw new ApplicationException("Unsupported version of Microsoft Internet Explorer!");
}
UInt32 mode = 11000; // Internet Explorer 11. Webpages containing standards-based !DOCTYPE directives are displayed in IE11 Standards mode.
switch (browserVersion)
{
case 7:
mode = 7000; // Webpages containing standards-based !DOCTYPE directives are displayed in IE7 Standards mode.
break;
case 8:
mode = 8000; // Webpages containing standards-based !DOCTYPE directives are displayed in IE8 mode.
break;
case 9:
mode = 9000; // Internet Explorer 9. Webpages containing standards-based !DOCTYPE directives are displayed in IE9 mode.
break;
case 10:
mode = 10000; // Internet Explorer 10.
break;
}
return mode;
}
Now, your scripts do run, but the <object> still doesn't get created (alert(MyObject.object) shows null). Finally, you'd need to implement IObjectSafety interface on your ActiveX object and site-lock it to only your very own HTML pages. Without proper IObjectSafety the object won't be getting created under default IE security settings. Without site-locking it might become a huge security threat, as any malicious script possibly could create and use your object outside the context of your application.
Updated to address the comment:
I've updated the project with your provided example, note that I had
made a change such that there is a C# button and a Javascript button
to fire the event. The JS button works, but C# does not fire. I'm
looking for a "Hello from: C# button" alert.
In your code, the myObject instance gets created and accessed exclusively from C#:
MyObject myObject = new MyObject();
// ...
private void button1_Click(object sender, EventArgs e)
{
// Call ActiveX
myObject.SayHello("C# Button");
}
This instance has nothing to do with the <object id="MyObject" onerror="window.objectLoadFailure = true" classid="clsid:7A5D58C7-1C27-4DFF-8C8F-F5876FF94C64"></object> instance that you create from HTML. They're two separate, unrelated objects. Your event handlers only work for the latter <object> instance. You don't even subscribe to any events on the new MyObject() instance.
If I understand your goal correctly, you need this:
private void button1_Click(object sender, EventArgs e)
{
// Call ActiveX
//myObject.SayHello("C# Button");
this.webBrowser1.Document.InvokeScript("eval",
new[] { "MyObject.SayHello('C# Button')" });
}
Now, the JavaScript event handler would get invoked and you'd see the "C# Button" alert.

How can I pass a JavaScript function to Silverlight?

I'm evaluating the JavaScript/Silverlight interop capabilities and have been able to create a Silverlight instance using JavaScript and call methods on it. However, I now need a way of passing a JavaScript callback function to Silverlight.
Simply passing a JavaScript function to a Silverlight method expecting an Action doesn't work although the error suggest that it's intended to. What am I missing? The exception details:
Microsoft JScript runtime error: System.ArgumentException: Cannot bind to the target method because its signature or security transparency is not compatible with that of the delegate type.
at System.Delegate.CreateDelegate(Type type, Object firstArgument, MethodInfo method, Boolean throwOnBindFailure)
at System.Windows.Hosting.ScriptingInterface.GetDelegateForScriptObject(Type eventHandlerType, ScriptObject obj)
at System.Windows.Browser.ScriptObject.ConvertTo(Type targetType, Boolean allowSerialization)
at System.Windows.Hosting.ScriptingInterface.GetScriptParamValueForType(ScriptParam scriptParam, Type desiredType)
at System.Windows.Hosting.ScriptingInterface.ConvertFromScriptParams(ParameterInfo[] parameters, ScriptParam[] args)
at System.Windows.Browser.ManagedObjectInfo.ScriptMethod.Invoke(ManagedObject obj, InvokeType invokeType, ScriptParam[] args)
at System.Windows.Browser.ManagedObjectInfo.Invoke(ManagedObject obj, InvokeType invokeType, String memberName, ScriptParam[] args)
at System.Windows.Hosting.ManagedHost.InvokeScriptableMember(IntPtr pHandle, Int32 nMemberID, Int32 nInvokeType, Int32 nArgCount, ScriptParam[] pArgs, ScriptParam& pResult, ExceptionInfo& pExcepInfo)
Without seeing your code I cannot say what you are doing wrong but I can describe what has worked for me in the past.
On the Silverlight side you need to register a class as a scriptable object. Then create a method that is marked as a ScriptableMember and takes a string that will be your passed in JavaScript method. I also added a method called InvokeCallback which will invoke the passed in javascript callback.
[ScriptableType]
public partial class Page : UserControl
{
private string jsCallback;
public Page()
{
InitializeComponent();
HtmlPage.RegisterScriptableObject("silverlightInterop", this);
}
[ScriptableMember]
public void RegisterCallback(string callback)
{
jsCallback = callback;
}
public boid InvokeCallback(string arg)
{
if(!string.IsNullOrEmpty(jsCallback))
{
System.Windows.Browser.HtmlPage.Window.Invoke(jsCallback, arg);
}
}
}
On the JavaScript side you can call the RegisterCallback method that you defined in Silverlight by grabbing the silverlight object on the page and calling the method off of the name "silverlightInterop" which we registered as the name of our scriptable object.
function jsCallback(someArg) {
alert(someArg);
}
var silverLightControl = document.getElementById("silverlightControl");
silverLightControl.content.silverlightInterop.RegisterCallback("jsCallback");
I hope this helps. I also have some sample code the demonstrates this which I wrote a while ago here
There is a simpler way to pass Javascript function to Silverlight. All values from javascript can be represented by the ScriptObject type, this includes a function. Its for this reason that the ScriptObject has a InvokeSelf method.
You can create a property as simple as:-
[ScriptableMember]
public ScriptObject Callback { get; set; }
Now lets say in Javascript we have this function:-
function sayHello(name)
{
alert("Hello " + name);
}
We can assign this to the property (assume the RegisterScriptableObject("Page", this) has been done) with this JS:-
document.getElementById("mySL").Content.Page.Callback = sayHello;
Now in Silverlight code we can invoke this Callback with:-
Callback.InvokeSelf("Freed");
Apparently, this does work if the using a delegate type of EventHandler (or EventHandler<>), but not for other delegate types.
My Code:
<!-- language: JavaScript -->
function sendText() {
return "Hi from Javascript!";
}
<!-- language: C# -->
string obj = HtmlPage.Window.Invoke("sendText", null) as string;
txtReturnData.Text = obj;
<!-- language: VB.Net -->
Dim obj As String = TryCast(HtmlPage.Window.Invoke("sendText", Nothing), String)
txtReturnData.Text = obj

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