如何检查程序集的类型是否为ComVisible

Question

我在为企业架构师写一个外接程序经理。

加载程序集(addin )时，我需要知道程序集中定义的哪些类型是COM可见的，因此我可以添加所需的注册表项来注册COM互操作。

到目前为止，我所拥有的是：

public EAAddin(string fileName):base()
{
    //load the dll
    this.addinDLL = Assembly.LoadFrom(fileName);
    //register the COM visible classes
    this.registerClasses(this.addinDLL);
    //load referenced dll's
    foreach (AssemblyName reference in this.addinDLL.GetReferencedAssemblies())
    {
          if (System.IO.File.Exists(
                 System.IO.Path.GetDirectoryName(this.addinDLL.Location) + 
                    @"\" + reference.Name + ".dll"))
          {
            Assembly referencedAssembly = System.Reflection.Assembly.LoadFrom(System.IO.Path.GetDirectoryName(this.addinDLL.Location) + @"\" + reference.Name + ".dll");
            //register the COM visible classes for the registered assembly
            this.registerClasses(referencedAssembly);
// ... more code ...
private void registerClasses (Assembly assembly)
{
    foreach (Type type in assembly.GetExportedTypes()) 
    {
            register(type, assembly);
    }
}

private void register(Type type, Assembly assembly)
{
    var attributes = type.GetCustomAttributes(typeof(ComVisibleAttribute),false);
    if  (attributes.Length > 0)
    {
        ComVisibleAttribute comvisible = (ComVisibleAttribute)attributes[0];
        if (comvisible.Value == true)
        {
            //TODO add registry keys here
        }
    }            
}

这不起作用，因为类型似乎不包含ComVisibleAttribute。

有人知道如何确定组件中的哪个ExportedTypes是COM可见的吗？

Answer 1

多亏了保罗的评论，我才弄明白了这一点。类型只有在与程序集默认值不同的情况下才具有ComVisibleAttribute。

因此，这个操作(对返回的Assembly.GetExportedTypes()类型之一进行调用)似乎可以做到这一点

/// <summary>
/// Check if the given type is ComVisible
/// </summary>
/// <param name="type">the type to check</param>
/// <returns>whether or not the given type is ComVisible</returns>
private bool isComVisible(Type type)
{
    bool comVisible = true;
    //first check if the type has ComVisible defined for itself
    var typeAttributes = type.GetCustomAttributes(typeof(ComVisibleAttribute),false);
    if  (typeAttributes.Length > 0)
    {
         comVisible = ((ComVisibleAttribute)typeAttributes[0]).Value;
    }
    else
    {
        //no specific ComVisible attribute defined, return the default for the assembly
        var assemblyAttributes = type.Assembly.GetCustomAttributes(typeof(ComVisibleAttribute),false);
        if  (assemblyAttributes.Length > 0)
        {
             comVisible = ((ComVisibleAttribute)assemblyAttributes[0]).Value;
        }
    }
    return comVisible;
}