Pra*_*eek 3 .net c# com idispatch
我想构建一个COM可见的 C#类,比如说DynamicComponent,它将通过COM 提供动态接口.
在内部,这个类将维护一个代表字典:
"GetTheAnswer" -> () => { return 42; }
"Add" -> (int a, int b) => { return a + b; }
...
客户端代码将是一些VBA.
这是我天真想象的工作流程:
DynamicComponent(至少得到Excel/VBA提供的存根)["GetTheAnswer" -> 1, "Add" -> 2]GetTheAnswer和Add我的第一个问题:这可能吗？
如果不是:为什么？
如果是的话:怎么样？
根据我对COM的了解,如果可能的话,IDispatch COM接口是我最好的朋友.
而且,根据我的理解,.Net 4 的ICustomQueryInterface接口也可以提供很大的帮助.
但是,如今COM并不是真正的尖端;)很难找到像代码样本这样的资源.
我发现了这个有趣的示例:https : //clrinterop.codeplex.com/releases/view/32350,它使用ICustomQueryInterface接口实现COM聚合
但它不是动态的,而是基于静态定义的类型和接口.
任何帮助将不胜感激.
谢谢.
公开IDispatchEx可以用于JavaScript,但我认为VBA不会使用它.AFAIK,VBA依赖于IDispatch后期绑定.此外,C#dynamic非常适合IDispatch在.NET端使用基于COM 的对象,但反之亦然.出于某种原因(.NET设计决定吗？),动态属性和方法ExpandoObject,并DynamicObject默认情况下不暴露在COM.
幸运的是,有一种方法可以覆盖它:通过实现IReflect接口.有关实施细节,请参阅此优秀博客文章.我自己看过将C#匿名类的属性暴露给COM,最后使用了IReflect.这是您向COM公开动态方法和属性的方法.形象地说,IReflect暴露给COM IDispatch.
另外,IExpando可以完成相同的工作IDispatchEx,因此JavaScript客户端可以添加新属性,以后可以通过托管代码进行访问.
[更新]下面是一个原型实现,它公开了一个DynamicComponent运行在里面的VBScript 的实例WebBrowser.它适用于VBScript,也应该适用于VBA.虽然,我怀疑VBA自动完成是否有效,或者有一种简单的方法来实现这样的功能.AFAIU,VBA自动完成依赖于COM类型库(获得通过IDispatch::GetTypeInfo),但我不认为当它实现.NET互操作程序引擎将生成动态类型库IDispatch通过IReflect(我可能是错的).此外,此实现对于逐个名称的查找区分大小写,应该调整,因为VB不区分大小写.
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Windows.Forms;
namespace WebBrowserApp
{
// https://stackoverflow.com/a/19067386/1768303
public partial class MainForm : Form
{
WebBrowser wb;
public MainForm()
{
InitializeComponent();
this.wb = new WebBrowser();
this.wb.Dock = DockStyle.Fill;
this.Controls.Add(this.wb);
this.wb.Visible = true;
var dynamicComponent = new DynamicComponent();
// make dynamicComponent available to VBScript
this.wb.ObjectForScripting = dynamicComponent;
// add a dynamic method "Convert"
dynamicComponent.SetMethod("Convert", new Func<int, string>((a) =>
{
MessageBox.Show("Convert called: " + a.ToString());
return a.ToString();
}));
this.Load += (s, e) =>
{
this.wb.DocumentText =
"<script type='text/vbscript'>\n" +
"Sub OnLoadHandler\n" +
" alert window.external.Convert(42)\n" +
"End Sub\n" +
"window.onload = GetRef(\"OnLoadHandler\")\n" +
"</script>";
};
}
}
#region DynamicComponent
[ComVisible(true), ClassInterface(ClassInterfaceType.None)]
public class DynamicComponent : System.Reflection.IReflect
{
readonly Dictionary<string, Delegate> _methods = new Dictionary<string, Delegate>();
public void SetMethod(string name, Delegate value)
{
_methods[name] = value;
}
static Exception NotImplemented()
{
var method = new StackTrace(true).GetFrame(1).GetMethod().Name;
Debug.Assert(false, method);
return new NotImplementedException(method);
}
#region IReflect
// IReflect
public FieldInfo GetField(string name, BindingFlags bindingAttr)
{
throw NotImplemented();
}
public FieldInfo[] GetFields(BindingFlags bindingAttr)
{
return new FieldInfo[0];
}
public MemberInfo[] GetMember(string name, BindingFlags bindingAttr)
{
throw NotImplemented();
}
public MemberInfo[] GetMembers(BindingFlags bindingAttr)
{
return new MemberInfo[0];
}
public MethodInfo GetMethod(string name, BindingFlags bindingAttr)
{
throw NotImplemented();
}
public MethodInfo GetMethod(string name, BindingFlags bindingAttr, Binder binder, Type[] types, ParameterModifier[] modifiers)
{
throw NotImplemented();
}
public MethodInfo[] GetMethods(BindingFlags bindingAttr)
{
return _methods.Keys.Select(name => new DynamicMethodInfo(name, _methods[name].Method)).ToArray();
}
public PropertyInfo[] GetProperties(BindingFlags bindingAttr)
{
return new PropertyInfo[0];
}
public PropertyInfo GetProperty(string name, BindingFlags bindingAttr, Binder binder, Type returnType, Type[] types, ParameterModifier[] modifiers)
{
throw NotImplemented();
}
public PropertyInfo GetProperty(string name, BindingFlags bindingAttr)
{
throw NotImplemented();
}
public object InvokeMember(string name, BindingFlags invokeAttr, Binder binder, object target, object[] args, ParameterModifier[] modifiers, System.Globalization.CultureInfo culture, string[] namedParameters)
{
if (target == this && invokeAttr.HasFlag(BindingFlags.InvokeMethod))
{
Delegate method;
if (!_methods.TryGetValue(name, out method))
throw new MissingMethodException();
return method.DynamicInvoke(args);
}
throw new ArgumentException();
}
public Type UnderlyingSystemType
{
get { throw NotImplemented(); }
}
#endregion
#region DynamicMethodInfo
// DynamicPropertyInfo
class DynamicMethodInfo : System.Reflection.MethodInfo
{
string _name;
MethodInfo _mi;
public DynamicMethodInfo(string name, MethodInfo mi)
: base()
{
_name = name;
_mi = mi;
}
public override MethodInfo GetBaseDefinition()
{
return _mi.GetBaseDefinition();
}
public override ICustomAttributeProvider ReturnTypeCustomAttributes
{
get { return _mi.ReturnTypeCustomAttributes; }
}
public override MethodAttributes Attributes
{
get { return _mi.Attributes; }
}
public override MethodImplAttributes GetMethodImplementationFlags()
{
return _mi.GetMethodImplementationFlags();
}
public override ParameterInfo[] GetParameters()
{
return _mi.GetParameters();
}
public override object Invoke(object obj, BindingFlags invokeAttr, Binder binder, object[] parameters, System.Globalization.CultureInfo culture)
{
return _mi.Invoke(obj, invokeAttr, binder, parameters, culture);
}
public override RuntimeMethodHandle MethodHandle
{
get { return _mi.MethodHandle; }
}
public override Type DeclaringType
{
get { return _mi.DeclaringType; }
}
public override object[] GetCustomAttributes(Type attributeType, bool inherit)
{
return _mi.GetCustomAttributes(attributeType, inherit);
}
public override object[] GetCustomAttributes(bool inherit)
{
return _mi.GetCustomAttributes(inherit);
}
public override bool IsDefined(Type attributeType, bool inherit)
{
return _mi.IsDefined(attributeType, inherit);
}
public override string Name
{
get { return _name; }
}
public override Type ReflectedType
{
get { return _mi.ReflectedType; }
}
}
#endregion
}
#endregion
}