您需要将回调委托从 C# 传递给 JavaScript。当 JavaScript 端的异步操作完成时,将回调此委托。什么信号完成自然是特定于您的脚本逻辑。它可以是 AJAX、DOM 或 Silverlight 事件。
正如@StephenCleary 在评论中指出的那样,您可以在脚本端进一步使用Deferred对象来方便地将完成事件包装在 JavaScript 中,就像您使用Task
(或TaskCompletionSource
) 在 C# 中包装事件一样。您仍然需要传递一个 C# 回调,当 deferred 得到解决时您将调用该回调。
在下面的代码中,我使用 JavaScript 计时器作为异步操作的示例。为简单起见,代码不使用延迟。
C#:
using Microsoft.Win32;
using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Threading.Tasks;
using System.Windows;
namespace WpfWebBrowser
{
public partial class MainWindow : Window
{
public MainWindow()
{
SetBrowserFeatureControl();
InitializeComponent();
this.Loaded += MainWindow_Loaded;
}
async void MainWindow_Loaded(object sender, RoutedEventArgs eventArg)
{
// navigate the browser
System.Windows.Navigation.LoadCompletedEventHandler loadedHandler = null;
var loadedTcs = new TaskCompletionSource<bool>();
loadedHandler = (s, e) =>
{
this.webBrowser.LoadCompleted -= loadedHandler;
loadedTcs.SetResult(true);
};
this.webBrowser.LoadCompleted += loadedHandler;
this.webBrowser.Navigate("http://localhost:81/callback.html");
await loadedTcs.Task;
// call the script method "scriptFuncAsync"
var asyncScriptTcs = new TaskCompletionSource<object>();
var oncompleted = new ScriptEventHandler((ref object returnResult, object[] args) =>
{
// we are here when the script has called us back
asyncScriptTcs.SetResult(args[0]);
});
this.webBrowser.InvokeScript("scriptFuncAsync", oncompleted);
await asyncScriptTcs.Task;
// show the result of the asyc call
dynamic result = asyncScriptTcs.Task.Result;
MessageBox.Show(result.outcome.ToString());
}
/// <summary>
/// ScriptEventHandler - an adaptor to call C# back from JavaScript or DOM event handlers
/// </summary>
[ComVisible(true), ClassInterface(ClassInterfaceType.AutoDispatch)]
public class ScriptEventHandler
{
[ComVisible(false)]
public delegate void Callback(ref object returnResult, params object[] args);
[ComVisible(false)]
private Callback _callback;
[DispId(0)]
public object Method(params object[] args)
{
var returnResult = Type.Missing; // Type.Missing is "undefined" in JavaScript
_callback(ref returnResult, args);
return returnResult;
}
public ScriptEventHandler(Callback callback)
{
_callback = callback;
}
}
/// <summary>
/// WebBrowser version control to enable HTML5
/// http://msdn.microsoft.com/en-us/library/ee330730(v=vs.85).aspx#browser_emulation
/// </summary>
void SetBrowserFeatureControl()
{
// http://msdn.microsoft.com/en-us/library/ee330720(v=vs.85).aspx
// FeatureControl settings are per-process
var fileName = System.IO.Path.GetFileName(Process.GetCurrentProcess().MainModule.FileName);
// make the control is not running inside Visual Studio Designer
if (String.Compare(fileName, "devenv.exe", true) == 0 || String.Compare(fileName, "XDesProc.exe", true) == 0)
return;
// Webpages containing standards-based !DOCTYPE directives are displayed in IE9/IE10 Standards mode.
SetBrowserFeatureControlKey("FEATURE_BROWSER_EMULATION", fileName, 9000);
}
void SetBrowserFeatureControlKey(string feature, string appName, uint value)
{
using (var key = Registry.CurrentUser.CreateSubKey(
String.Concat(@"Software\Microsoft\Internet Explorer\Main\FeatureControl\", feature),
RegistryKeyPermissionCheck.ReadWriteSubTree))
{
key.SetValue(appName, (UInt32)value, RegistryValueKind.DWord);
}
}
}
}
XAML:
<Window x:Class="WpfWebBrowser.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<WebBrowser Name="webBrowser"/>
</Window>
http://localhost:81/callback.html
:
<!DOCTYPE html>
<html>
<head>
<title></title>
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<script>
window.scriptFuncAsync = function (oncompleted) {
// do something async, use timer
setTimeout(function () {
info.innerHTML = "Async operation completed.";
oncompleted({ outcome: 42 });
}, 2000);
}
</script>
</head>
<body>
<span>Async Script Test Page</span><br>
<span id="info"></span>
</body>
</html>
[更新]:
下面是一个更复杂的脚本,说明了 jQuery 的Deferred/Promise 模式的使用。它执行两个异步操作(并行),然后在两个操作完成时回调 C#(因此它们的承诺已经解决)。
<!DOCTYPE html>
<html>
<head>
<title></title>
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<script src="//ajax.googleapis.com/ajax/libs/jquery/2.0.3/jquery.min.js"></script>
<script>
window.scriptFuncAsync = function (oncompleted) {
// do something async, use timer
var promise1 = (function () {
var deferred = $.Deferred();
setTimeout(function () {
deferred.resolve("Async timeout completed.");
}, 3000);
return deferred.promise();
})();
promise1.done(function () {
output("promise1 resolved.");
});
var promise2 = $.ajax({ url: "http://www.html5rocks.com/en/resources" });
promise2.done(function () {
output("promise2 resolved.");
});
$.when(promise1, promise2).then(function(result1, result2) {
output("result1: " + result1);
output("result2: " + result2.toString().substr(0, 100) + "...");
oncompleted({ outcome: 42 });
});
function output(str) {
if (!info.firstChild)
info.appendChild(document.createTextNode(""));
info.firstChild.data += str + "\n";
}
};
</script>
</head>
<body>
<span>Async Script Test Page</span><br>
<pre id="info"></pre>
</body>
</html>