Getting System.Argument Exception when invoking a delegate

[Nony Buz]

My objective is simply: Notify a form when a image file has been
created in a directory. First there is a basic interface for the
callback function:

public interface INewImageNotify
{
void notify_NewImage (string imageName);
}

Then there is the delegate:

delegate void DelegateNewImag e(string imageName);

The form implements this interface. Then there is a separate
class that manages the FileSystemWatch er. The form creates one of
these class, the constructor looks like this:

public ImageMonitor(st ring soureDir, string filter,
ImageSelectorFo rm form)
{
m_form = form;
m_watcher = new FileSystemWatch er(sourceDir, filter);

m_watcher.Notif yFilter = NotifyFilters.L astAccess |
NotifyFilters.L astWrite | NotifyFilters.F ileName |
NotifyFilters.D irectoryName;

m_watcher.Creat ed += new FileSystemEvent Handler(this. OnCreate);
m_watcher.Enabl eRaisingEvents = true;
}

then this class implements OnCreate(...):

private void OnCreate(object source, FileSystemEvent Args e)
{
FileInfo fileInfo = new FileInfo(e.Full Path);
if( String.Compare( fileInfo.Extens ion, ".jpg") == 0 )
{
notify_NewImage (e.FullPath);
}
}

And the class also implements the INewImageNotify interface:

public void notify_NewImage (string imageName)
{
if ((m_form != null) && (m_form.Visible ))
{
try
{
object[] args = new object[1];
args[0] = imageName;

m_form.Invoke( new DelegateNewImag e( m_form.notify_N ewImage), args);
}
catch( System.Argument Exception e)
{
Debug.WriteLine ( e.ToString());
}
}
}

The first time this notify_NewImage () gets called, all is well.
The second time through, the Invoke throws
System.Argument Exception. I don't get it! Why does it work once?
Why isn't it working at all after that? Is there a better
approach?

[Nony Buz]

I found the problem, but don't know the fix. The problem is that
FileSystemWatch er is too fast. It is notifying as soon as the
file is created, in my case, before the copy is complete. Thus,
in the form where it is loaded, the load fails. How do I find out
when the file is completely copied?

On 2005-04-05, Nony Buz <no**@dwtty.com > wrote:

My objective is simply: Notify a form when a image file has been
created in a directory. First there is a basic interface for the
callback function:

public interface INewImageNotify
{
void notify_NewImage (string imageName);
}

Then there is the delegate:

delegate void DelegateNewImag e(string imageName);

The form implements this interface. Then there is a separate
class that manages the FileSystemWatch er. The form creates one of
these class, the constructor looks like this:

public ImageMonitor(st ring soureDir, string filter,
ImageSelectorFo rm form)
{
m_form = form;
m_watcher = new FileSystemWatch er(sourceDir, filter);

m_watcher.Notif yFilter = NotifyFilters.L astAccess |
NotifyFilters.L astWrite | NotifyFilters.F ileName |
NotifyFilters.D irectoryName;

m_watcher.Creat ed += new FileSystemEvent Handler(this. OnCreate);
m_watcher.Enabl eRaisingEvents = true;
}

then this class implements OnCreate(...):

private void OnCreate(object source, FileSystemEvent Args e)
{
FileInfo fileInfo = new FileInfo(e.Full Path);
if( String.Compare( fileInfo.Extens ion, ".jpg") == 0 )
{
notify_NewImage (e.FullPath);
}
}

And the class also implements the INewImageNotify interface:

public void notify_NewImage (string imageName)
{
if ((m_form != null) && (m_form.Visible ))
{
try
{
object[] args = new object[1];
args[0] = imageName;

m_form.Invoke( new DelegateNewImag e( m_form.notify_N ewImage), args);
}
catch( System.Argument Exception e)
{
Debug.WriteLine ( e.ToString());
}
}
}

The first time this notify_NewImage () gets called, all is well.
The second time through, the Invoke throws
System.Argument Exception. I don't get it! Why does it work once?
Why isn't it working at all after that? Is there a better
approach?

[MuZZy]

Nony Buz wrote:

I found the problem, but don't know the fix. The problem is that
FileSystemWatch er is too fast. It is notifying as soon as the
file is created, in my case, before the copy is complete. Thus,
in the form where it is loaded, the load fails. How do I find out
when the file is completely copied?
Put the copying routine in a separate thread(so that it won't freeze the app while waiting),
and in it check for ability to copy file periodically, say, once every second or so...
Put file cpying func in try{}catch{} so it won't fire every time it fails.

Something like this:

void ThreadFunc()
{
bool bOk = false;
while (!bOk)
{
try
{
Fiel.Copy(strFi leName, strNewFileName) ;
bOk = true;
}
catch(IOExcepti on)
{Thread.Sleep(1 000)); // Not correct - don't remember how to call sleep here, but yo u get the idea
}
}
Or to improve, create a thread class and include a callback/delegate function which will fire when
thread is done.

I'm not a "pro" with threads, so maybe you know better way of dealing with threads here, but the
idea is as above. I remember using it myself in a project a year ago - worked perfect

Hope it helps,
Andrey

On 2005-04-05, Nony Buz <no**@dwtty.com > wrote:

My objective is simply: Notify a form when a image file has been
created in a directory. First there is a basic interface for the
callback function:

public interface INewImageNotify
{
void notify_NewImage (string imageName);
}

Then there is the delegate:

delegate void DelegateNewImag e(string imageName);

The form implements this interface. Then there is a separate
class that manages the FileSystemWatch er. The form creates one of
these class, the constructor looks like this:

public ImageMonitor(st ring soureDir, string filter,
ImageSelector Form form)
{
m_form = form;
m_watcher = new FileSystemWatch er(sourceDir, filter);

m_watcher.Notif yFilter = NotifyFilters.L astAccess |
NotifyFilters.L astWrite | NotifyFilters.F ileName |
NotifyFilters.D irectoryName;

m_watcher.Creat ed += new FileSystemEvent Handler(this. OnCreate);
m_watcher.Enabl eRaisingEvents = true;
}

then this class implements OnCreate(...):

private void OnCreate(object source, FileSystemEvent Args e)
{
FileInfo fileInfo = new FileInfo(e.Full Path);
if( String.Compare( fileInfo.Extens ion, ".jpg") == 0 )
{
notify_NewImage (e.FullPath);
}
}

And the class also implements the INewImageNotify interface:

public void notify_NewImage (string imageName)
{
if ((m_form != null) && (m_form.Visible ))
{
try
{
object[] args = new object[1];
args[0] = imageName;

m_form.Invoke( new DelegateNewImag e( m_form.notify_N ewImage), args);
}
catch( System.Argument Exception e)
{
Debug.WriteLine ( e.ToString());
}
}
}

The first time this notify_NewImage () gets called, all is well.
The second time through, the Invoke throws
System.Argume ntException. I don't get it! Why does it work once?
Why isn't it working at all after that? Is there a better
approach?