Asyncronous MDIchild loading

[Kirk_G]

I have a MDI application in C# that loads image data in MDI windows. The child form has a constructor with a filename parameter for the image data. If I try to open large files or files over a network it can be slow and halt the parent program. Is there a way to asyncronously load MDI windows? I have tried creating a delegate with the child forms signature, calling the delegates BeginInvoke method with a callback method that sets the child forms parent to "this" but there seems to be some fundamental problem with this idea. Everything is great up to the point where I try to set the MDIparent parameter to "this". Here is a snipet:

public delegate ChildForm Async_ChildFormDelegate(string filename, bool logdata);

//Now inside of ParentForm class
public void LoadUnloggedData()
{
   OpenFileDialog mydialog = new OpenFileDialog();
mydialog.Title = @"Open Un-Logged Images";
mydialog.Multiselect = true;
if(mydialog.ShowDialog() == DialogResult.OK)
{
	foreach (String name in mydialog.FileNames)
	{
		Async_ChildFormDelegate AsyncLoadOCT = new Async_ChildFormDelegate(Async_LoadData);
		IAsyncResult asyncResult = AsyncLoadOCT.BeginInvoke(name,true,new AsyncCallback(CallbackHandler),AsyncLoadOCT);
	}

}
}

public ChildForm Async_LoadData(string filename, bool logdata)
{
ChildForm newOCT = new ChildForm(filename,logdata);

return newOCT;
}

public void CallbackHandler(IAsyncResult result)
{
Async_ChildFormDelegate childForm = (Async_ChildFormDelegate)result.AsyncState;

ChildForm newOCT = childForm.EndInvoke(result);

newOCT.MdiParent = this;
// Set Cursor Size
newOCT.Xsize = sizeX;
newOCT.Ysize = sizeY;
// Display the new form.
newOCT.Show();
}

 

Everything is fine until

newOCT.MdiParent = this;

at which point the program jumps back up the top of the callbackhandler method, reruns the first 2 lines and leaves the method. The parent window come back up with no MDIchild loaded. Any ideas? Thanks

Kirk

[Kirk_G]

Here is an updated code snipet from a simpler example I created just to test this point

public delegate childForm AsyncLoadMDIDelegate(string filename);

 

private void openItem_Click(object sender, System.EventArgs e)
	{
		OpenFileDialog openDialog = new OpenFileDialog();
		openDialog.Title = @"Select Image Files";
		openDialog.Multiselect = true;

		if(openDialog.ShowDialog() == DialogResult.OK)
		{
			foreach(string name in openDialog.FileNames)
			{
				//This commented out section works just fine
				//childForm newChild = new childForm(name);
				//newChild.MdiParent = this;
				//newChild.Show();

				//Not sure why this doesn't work
				AsyncLoadMDIDelegate loadMDIDelegate = new AsyncLoadMDIDelegate(this.loadMDI);
				IAsyncResult asyncResult = loadMDIDelegate.BeginInvoke(name,new AsyncCallback(this.CallBackHandler),loadMDIDelegate);
			}
		}
	}

	public void CallBackHandler(IAsyncResult result)
	{
		AsyncLoadMDIDelegate loadMDIDelegate = (AsyncLoadMDIDelegate)result.AsyncState;
		childForm newChild = loadMDIDelegate.EndInvoke(result);
		newChild.MdiParent = this; //This is where the program doesn't work
		newChild.Show();
	}

	public childForm loadMDI(string filename)
	{
		childForm newChild = new childForm(filename);
		return newChild;
	}

 

Can anyone tell me why this doesn't asyncronously load MDI wondows. I don't get any exceptions, they just don't show up. The newChild.Show(); never runs because it never gets past the newChild.MdiParent = this; never works? Any help would be appriciated. Thanks

Kirk

[Kirk_G]

Can anyone tell me if I'm missing something obvious here or is theresome fundamental reason this can't be done? Thanks

[Kirk_G]

anyone?