I think that the common knowledge is that you need Winforms to be able to use ActiveX control. Well, not entirely true. You need winforms-like message loop and STAThread.
Let's start by presenting the design of my solution. I prefer to seperate code to as many layers as needed when dealing with something unknown so you may find some layers redundant. I encourage you to help me improve the solution to find the equilibrium.
Please remember about the need to implement the IDisposable interface in all outer layers if needed.
ActiveXCore - class containing an ActiveX control declared as a private field. In this class you use just code like you would in Winforms.
CoreAPI - an internal API class that exposes the methods of ActiveXCore. I found out that it is good to mark the methods with [STAThreadAttribute] as I had some problems without it, though it may be specific to this case only.
PublicAPI - my main library class that will be called in the referencing projects.
Now, in the ActiveXCore there are really no guidelines.
In CoreAPI the sample method would be
[STAThreadAttribute]
internal bool Init()
{
try
{
_core = new ActiveXCore();
//...
return true;
}
catch (System.Runtime.InteropServices.COMException)
{
//handle the exception
}
return false;
}
To be able to properly run these you would need Winforms like message loop like this (the desing is not mine at all, I just slightly modified the code). You don't need the Winforms project type, but you have to reference System.Windows.Forms assembly
public class MessageLoopApartment : IDisposable
{
public static MessageLoopApartment Apartament
{
get
{
if (_apartament == null)
_apartament = new MessageLoopApartment();
return _apartament;
}
}
private static MessageLoopApartment _apartament;
private Thread _thread; // the STA thread
private TaskScheduler _taskScheduler; // the STA thread's task scheduler
public TaskScheduler TaskScheduler { get { return _taskScheduler; } }
/// <summary>MessageLoopApartment constructor</summary>
public MessageLoopApartment()
{
var tcs = new TaskCompletionSource<TaskScheduler>();
// start an STA thread and gets a task scheduler
_thread = new Thread(startArg =>
{
EventHandler idleHandler = null;
idleHandler = (s, e) =>
{
// handle Application.Idle just once
Application.Idle -= idleHandler;
// return the task scheduler
tcs.SetResult(TaskScheduler.FromCurrentSynchronizationContext());
};
// handle Application.Idle just once
// to make sure we're inside the message loop
// and SynchronizationContext has been correctly installed
Application.Idle += idleHandler;
Application.Run();
});
_thread.SetApartmentState(ApartmentState.STA);
_thread.IsBackground = true;
_thread.Start();
_taskScheduler = tcs.Task.Result;
}
/// <summary>shutdown the STA thread</summary>
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool disposing)
{
if (_taskScheduler != null)
{
var taskScheduler = _taskScheduler;
_taskScheduler = null;
// execute Application.ExitThread() on the STA thread
Task.Factory.StartNew(
() => Application.ExitThread(),
CancellationToken.None,
TaskCreationOptions.None,
taskScheduler).Wait();
_thread.Join();
_thread = null;
}
}
/// <summary>Task.Factory.StartNew wrappers</summary>
public void Invoke(Action action)
{
Task.Factory.StartNew(action,
CancellationToken.None, TaskCreationOptions.None, _taskScheduler).Wait();
}
public TResult Invoke<TResult>(Func<TResult> action)
{
return Task.Factory.StartNew(action,
CancellationToken.None, TaskCreationOptions.None, _taskScheduler).Result;
}
public Task Run(Action action, CancellationToken token)
{
return Task.Factory.StartNew(action, token, TaskCreationOptions.None, _taskScheduler);
}
public Task<TResult> Run<TResult>(Func<TResult> action, CancellationToken token)
{
return Task.Factory.StartNew(action, token, TaskCreationOptions.None, _taskScheduler);
}
public Task Run(Func<Task> action, CancellationToken token)
{
return Task.Factory.StartNew(action, token, TaskCreationOptions.None, _taskScheduler).Unwrap();
}
public Task<TResult> Run<TResult>(Func<Task<TResult>> action, CancellationToken token)
{
return Task.Factory.StartNew(action, token, TaskCreationOptions.None, _taskScheduler).Unwrap();
}
}
And then you can provide methods like that
public bool InitLib()
{
return MessageLoopApartment.Apartament.Run(() =>
{
ca = new CoreAPI();
bool initialized = ca.Init();
}, CancellationToken.None).Result;
}
of if the method would be void
public void InitLib()
{
MessageLoopApartment.Apartament.Run(() =>
{
ca = new CoreAPI();
ca.Init();
}, CancellationToken.None).Wait();
}
As for the auto registering I designed something like this (I call it from CoreAPI)
internal static class ComponentEnvironment
{
internal static void Prepare()
{
CopyFilesAndDeps();
if (Environment.Is64BitOperatingSystem)
RegSvr64();
RegSvr32(); //you may notice no "else" here
//in my case for 64 bit I had to copy and register files for both arch
}
#region unpack and clean files
private static void CopyFilesAndDeps()
{
//inspect what file you need
}
#endregion unpack and clean files
#region register components
private static void RegSvr32()
{
string dllPath = @"xxxx86xxx.dll";
Process.Start("regsvr32", "/s " + dllPath);
}
private static void RegSvr64()
{
string dllPath = @"xxxx64xxx.dll";
Process.Start("regsvr32", "/s " + dllPath);
}
#endregion register components
}
I spent many days and nights to design this reusable pattern so I hope it will help someone.
