在 C# 中创建 COM/ActiveXObject，从 JScript 中使用，带有简单的事件

Create COM/ActiveXObject in C#, use from JScript, with simple event(在 C# 中创建 COM/ActiveXObject，从 JScript 中使用，带有简单的事件)

问题描述

我想在 C# 中创建一个 COM 对象，并通过 JScript 中的 IDispatch 使用它.这部分很简单.

I'd like to create a COM object in C#, and use it via IDispatch from JScript. That part is pretty simple.

我还想在 COM 对象上实现简单的回调，类似于可在浏览器中使用的 XmlHttpRequest 对象公开的事件.该模型允许 Javascript 像这样附加事件处理程序:

I also want to implement simple callbacks on the COM object, similar to the event exposed by the XmlHttpRequest object that is usable in a browser. That model allows Javascript to attach event handlers like this:

var xmlhttp = new ActiveXObject("MSXML.XMLHTTP"); 
xmlhttp.onReadyStateChange = function() {
  ...
};

我希望我的客户端 JScript 代码如下所示:

I want my client-side JScript code to look like this:

var myObject = new ActiveXObject("MyObject.ProgId");
myObject.onMyCustomEvent = function(..args here..) { 
   ...
};

C# 代码是什么样的?我想要一般情况 - 我希望能够将参数传递回 Javascript fn.

What does the C# code look like? I'd like the general case - I'd like to be able to pass arguments back to the Javascript fn.

我见过 如何使用 C# 编写的 ActiveX 控件在点击时在 JavaScript 中引发事件? ，但那里的答案看起来真的很难实现，而且使用起来也很复杂.

I've seen How can I make an ActiveX control written with C# raise events in JavaScript when clicked? , but the answers there look really complicated to implement, and complicated to use.

从这篇文章看来，XMLHttpRequest事件不是COM 事件.onreadystatechange 是 IDispatch 类型的属性.当脚本客户端将该属性设置为函数时，JScript 将其编组为 IDispatch 对象.

From this article, it seems that XMLHttpRequest events are not COM events. The onreadystatechange is a property of type IDispatch. When script clients set that property to a function, JScript marshals it as an IDispatch object.

剩下的唯一问题是从 C# 调用 IDispatch.

The only problem that remains is then to invoke the IDispatch from C#.

推荐答案

既然是COM，就先定义一个接口.让我们保持简单.

Since it's COM, start by defining an interface. Let's keep it simple.

[Guid("a5ee0756-0cbb-4cf1-9a9c-509407d5eed6")]
[InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
public interface IGreet
{
    [DispId(1)]
    string Hello(string name);

    [DispId(2)]
    Object onHello { get; set; }
}

然后，实现:

[ProgId("Cheeso.Greet")]
[ComVisible(true)]
[Guid("bebcfaff-d2f4-4447-ac9f-91bf63b770d8")]
[ClassInterface(ClassInterfaceType.None)]
public partial class Greet : IGreet
{
    public Object onHello { get; set; }

    public String Hello(string name)
    {
        var r = FireEvent();
        return "Why, Hello, " + name + "!!!" + r;
    }
}

主要技巧是 FireEvent 方法.这对我有用.

The main trick is the FireEvent method. This worked for me.

    private string FireEvent()
    {
        if (onHello == null) return " (N/A)";
        onHello
            .GetType()
            .InvokeMember
            ("",
             BindingFlags.InvokeMethod,
             null,
             onHello,
             new object [] {});

        return "ok";
    }

一起编译，用 regasm 注册:

Compile that all together, register it with regasm:

%NET64%
egasm.exe Cheeso.Greet.dll /register /codebase

...然后像这样从 JScript 中使用它:

...And then use it from JScript like this:

var greet = new ActiveXObject("Cheeso.Greet"), response;
greet.onHello = function() {
    WScript.Echo("onHello (Javascript) invoked.");
};
response = greet.Hello("Fred");
WScript.Echo("response: " + response);

它有效.

您也可以从 VBScript 中调用它:

You can also call it from VBScript:

Sub onHello ()
    WScript.Echo("onHello (VBScript) invoked.")
End Sub

Dim greet
Set greet = WScript.CreateObject("Cheeso.Greet")
greet.onHello = GetRef("onHello")
Dim response
response = greet.Hello("Louise")
WScript.Echo("response: " &  response)

<小时>

要使用这种方法将参数从 C# 传递回 JScript，我认为对象需要是 IDispatch，但当然您可以将简单的值作为字符串、int 等封送返回，这些值按照您的预期进行封送.

---

To pass parameters back from C# to JScript with this approach, I think objects need to be IDispatch, but of course you can send back simple values marshaled as string, int, and so on which are marshaled as you would expect.

例如，修改 C# 代码以返回对自身的引用，以及数字 42.

For example, modify the C# code to send back a reference to itself, and the number 42.

        onHello
            .GetType()
            .InvokeMember
            ("",
             BindingFlags.InvokeMethod,
             null,
             onHello,
             new object [] { this, 42 });

然后，你可以像这样在 jscript 中得到它:

Then, you can get that in jscript like so:

greet.onHello = function(arg, num) {
    WScript.Echo("onHello (Javascript) invoked.");
    WScript.Echo("  num = " + num + "  stat=" + arg.status);
};

或者在 VBScript 中像这样:

Or in VBScript like so:

Sub onHello (obj, num)
    WScript.Echo("onHello (VBScript) invoked. status=" & obj.status )
    WScript.Echo("  num= " & num)
End Sub

注意:您可以定义您的 jscript 事件处理函数，以在调用事件"时接受比 C# 对象发送的更少的参数.根据我的经验，您需要在 VBScript 中设计事件处理程序以显式接受正确数量的参数.

NB: You can define your jscript event handler function to accept fewer args than are sent by the C# object when invoking the "event". In my experience you need to design the event handler in VBScript to explicitly accept the correct number of arguments.

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