Re: The Objective / Solution - C# Discussion Boards

Drag Drop - Simple Theory - Simple Solution?

16-Dec-03 4:07

It doesn't have anything to do with the size of the assembly. You've found a pattern, but a pattern unique to you. That happens to us with assemblies of all sizes, and assemblies that are referenced by others both frequently and infrequently.

This problem exists in both VS.NET 2002 and 2003. While I too hope they fix it, it's not looking too good. I know a lot of people - including myself - have posted this bug to their newsgroups, but you should as well (use the NNTP server msnews.microsoft.com or the web-based news reader on their site in various places). Every mention should help.

Tristan Rhodes16-Dec-03 2:58

Re: Drag Drop - Simple Theory - Simple Solution?

16-Dec-03 2:58

Would it be possible to combine the FileFormat.FileDrop with an automatic file construction?

For instance, when the mouse button is pressed, and dragdrop is intiated, when the mouse pointer leaves the managed enviroment, the program constructs the dragged item in the root / temp directory, and forwards the file name (With path) to the arguments used by the dragdrop, thereby, the file is created in the temp directory, and then moved.

This would negate the need to worry about interfacing with COM, and simplify the whole process.
The only things I am uncertain about are:

1) How to determine when the mouse has left the managed enviroment. (X,Y mouse coorinates mapped to the form size? This could be process intensive, so i'm not sure).

2) Deleting a file. Can it be done without security settings, or is that irrelivent?

3) Would it be worth constructing the file to begin with anyway? It could disrupt the drag drop if the file is large or there are many of them. Is there any way to manage a file constructing without chewing up 100% of the CPU? (Thread perhaps?)

4) What about multiple files? Can the drag drop method handle multiple objects? Construct 5-6 objects by stream, and then enable the drag and drop?

There are a number of problems I can see with this method, but there must be some way to manage it. If the file is being written to or is still open when the drop command is sent, then it won't work for one.

I'm just toying with ideas here.

Any thoughts?

Cata

Tristan Rhodes16-Dec-03 3:05

Re: Drag Drop - Simple Theory - Simple Solution?

16-Dec-03 3:05

Unless, I don't perform the dragdrop operation immediately, and when the file is completed, I could then pull the file path from the COM method, and move the file using that?

Heath Stewart16-Dec-03 3:42

16-Dec-03 3:42

The_Catalyst wrote:
4) What about multiple files? Can the drag drop method handle multiple objects? Construct 5-6 objects by stream, and then enable the drag and drop?

Yes it can. The DataFormats.FileDrop clipboard format is a managed string[] array, which gets marshaled correctly so that Windows can understand it.

You know, in as many questions and answers that have been posted about your problem, you have never once mentioned what you are trying to do. Perhaps someone has a better solution overall than what you are trying to do. This may help things.

Also, yes, creating the files when the mouse leaves the form (which is possible) would be incredibly inefficient and would probably just piss-off your users since the CPU would spike and their shell would appear to hang for a while. The stream way I've mentioned before is about the only way to know when something is requesting the file(s) that you are providing.

The Objective / Solution

16-Dec-03 4:27

I have a list view, and a tree view. They are synchronised (The active folder in the tree view displays it's contents (an ArrayList assigned the the TAG object) in the list view).

I can drag stuff between folders in the tree view, and rearange the list view all well and good.

It's similar to winzip with winMPQ elements, only I intend to add methods to the archive to automaticaly present a content map to a program that wishes to access it.

While I have written a program to import and export files and objects via a fileDialogBox, i would like to implement drag and drop of list view objects (or the data they represent) into the list / folder view both two and from the windows enviroment.

I have the dragging from windows enviroment working, extracting the data and adding it to the TAG, then refreshing the listview, and performing an Icon lookup based on the extention.

The objects I would like to drag out of the enviroment will have their data extracted and assigned to ObjectData.Data, and the filepath will be constructed from *name*.*extention*.

<br />
struct ObjectData<br />
{<br />
object data;<br />
string name;<br />
string extention;<br />
}

Looking at it now, it may well be worth my while using the predefined ObjectData object instead of my own version. That should not be too difficult to accomplish, but which version should I use? COM, or .NET?

I can implement the COM object that I need, but I am unsure of how to manage the transition between COM DataObjects and the .NET version. When, where and how, if at all, should they be replaced? Only for drops outside the enviroment? Or inside as well? Will I have to handle the managed COM objects for internal drops if I want to use it at all?

Cata

Heath Stewart16-Dec-03 5:04

16-Dec-03 5:04

You'd probably need to use the COM IDataObject, but you don't translate this to or form the .NET version. It's all P/Invoked calls (like the native DoDragDrop function), structures (like STDMEDIUM and FORMATETC), and interfaces (like IDataObject, IDragSource, and IStrea). The .NET drag-n-drop isn't used in this solution. It is an overly simplified implementation that won't do what you need. I've actually read the IL behind these classes and .NET uses this same approach - eventually the IDataObject is transformed into COM's and the native methods are used, but these are internal and you cannot access them except through reflection (and that would be even harder).

Tristan Rhodes16-Dec-03 5:27

16-Dec-03 5:27

So i will just have to handle the COM versions? I can't use the .NET drag and drop at all, even for internal moves?

(Just making sure I understand you :p )

Cata

Heath Stewart16-Dec-03 5:29

16-Dec-03 5:29

You could use it for internal moves and you can even use the events to trigger the COM routines, but it will be hard distinguishing whether or not you'll need to do .NET or COM routines. Either way, the end result is the same. Remember that the .NET routines, interfaces, etc., are built on top of the Win32 drag-n-drop, so you can still use the .NET events for dropping in your application, but you should use the COM routines to pack the data how you want.

Tristan Rhodes16-Dec-03 6:16

16-Dec-03 6:16

So overwrite the DoDragDrop method, replace the structures with managed COM structures etc, and just let .NET interact with it in the way it was designed.

The only problem I can see is, will .NET recognise the new method and handle the mouse pointer shape automaticaly? Or is that windows that manges that and determines whether it is a dropable location?

I'm going to assume it's windows and get on with it at some point when I feel better.

God I hate Colds. They ruin thought processes Frown | :(

Cat

Heath Stewart16-Dec-03 6:21

16-Dec-03 6:21

No, don't override DoDragDrop. For one, it's not virtual (meaning you have to declare it with the new) keyword. Second, the data parameter expects an IDataObject (or temporary, unformatted Object) from .NET - not COM (type Types, while named the same, are still different Types).

You need to P/Invoke the native DoDragDrop functions. I only meant that you could initiate drag-n-drop using the same event handlers but using the P/Invoked code. Your drop targets can use the managed drag-n-drop events because the data object will by seen by .NET the same way. If you want to support the same formats as the DataFormats class fields, just use the same format IDs as they have (which you can find by using the same strings (check the fields' values) or the IDs, which you can get from the Win32 headers).

Tristan Rhodes16-Dec-03 6:33

Re: Rich Text box problem

16-Dec-03 6:33

Gotcha.

I shall crack on with it.

I'll let you know how I go, and when I got it working, I suppose the lease I could do is stick the code up on CP.

Thanks again for helping me get my head around that one.

I just had the biggest "AAAAAHHHHH!!!" moment when the penny dropped.

Cata

Rich Text box problem

Abhi158116-Dec-03 2:43

Abhi1581

16-Dec-03 2:43

I have a Rich Text Box Control. In which i want that only text along with its formatting(bold, color etc) be pasted. But it should discard IF clipboard item contains Image.
I tried using
if(!(Clipboard.GetDataObject().GetDataPresent(DataFormats.Bitmap)))
{
Clipboard.GetDataObject().GetFormats();
this.Paste();
}

but does not allow Image to be pasted but if data to be pasted contains Image and Text both it fails to restrict.
I also tried with DataFormats.Text but then only text is pasted and formatting is lost. Can anybody help me.

Heath Stewart16-Dec-03 3:36

How to report changes in FTP server?

16-Dec-03 3:36

There are different types of image data formats you should check, not just DataFormats.Bitmap. That only specifies a Windows Bitmap and while some programs may put both, for example, JPG and its uncompressed BMP format in the data object, some might not. So make sure you check that there are no images. This would be an exclusive approach.

You could also use an inclusive approach. If you only want formatted or plain text inserted, that check for the existence of those and only those by using DataObject.GetFormats and making sure that all the string array elements are what you want (which reminds me, your call Clipboard.GetDataObject.GetFormats() is useless since you aren't using it's return value - is just a waste of instructions). This would be an inclusive approach and can better limit what you accept in your RichTextBox. Just check for DataFormats.Rtf, DataFormats.Text, DataFormats.UnicodeText, and/or DataFormats.OemText.

The latter method is probably better because the clipboard formats (which are also used in drag-n-drop routines) are not limited to what's in the DataFormats class. Those are just some common ones that are pre-registered by Windows and understandable in .NET. Applications can easily make up their own formats and there are other common formats that the RichTextBox might understand.

mkomasi16-Dec-03 2:43

mkomasi

16-Dec-03 2:43

Hi,

I have an FTP server by some users. Each user has a folder and can add or delete a file in his specified folder.
Now I want that I'm notifed by email when a user makes any change in his folder.
Can I use C# to do this situation?
Does FTP server provide me this situation or I have to develop a program?

regards,
Mehdi

Re: How to report changes in FTP server?

Heath Stewart16-Dec-03 3:24

shortcut on text-less button

16-Dec-03 3:24

Doing this via FTP would be difficult - if even possible. About the only way is to poll the folders and check for recent changes. A better way would be to write a program that uses the FileSystemWatcher component to watch the directories on the server (i.e., not via FTP but on the file system itself) and alerts you of changes.

troels_sorensen16-Dec-03 2:08

troels_sorensen

16-Dec-03 2:08

Hi.

I've got a button with no text (only and icon) and I need a shortcut key (accelerator key) to the button.
Normally i would do something like "Cl&ose" to use the "o" as a shortcut, but my button has no text, so how do i accimplish this? Hmmm | :|

Re: shortcut on text-less button

Heath Stewart16-Dec-03 3:23

detecting and editing extended properties

16-Dec-03 3:23

Set KeyPreview to true on your Form that contains the button and handle the KeyDown or KeyUp event, which will give you the active modifier keys (Alt, Ctrl, and/or Shift) and the key that was pressed in a KeyEventArgs passed to the event handler.

pekai15-Dec-03 23:50

pekai

15-Dec-03 23:50

I extended my menuitem with an additional property. it works well with the property editor.

now I need write some code to detect and change the extended properties. I tried using the folowing code but it is not "detecting" the extended properties.

<br />
PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(menuItem1);<br />
foreach (PropertyDescriptor myProperty in properties)<br />
    textBox1.Text += myProperty.Description.ToString() + '\n';<br />

how can I detect and edit extended properties?
thank you...

Peter Kaiser

Heath Stewart16-Dec-03 3:21

16-Dec-03 3:21

"detect and edit" is rather ambiguous and perhaps you could clarify.

If you are talking about getting and setting values, see the PropertyDescriptor.GetValue and PropertyDescriptor.SetValue, which both use the PropertyDescriptor for your Type, and you pass your actual object (menuItem1) so that you get the value for that property on that object. See the SDK documentation for those two methods for more information and examples.

pekai16-Dec-03 3:50

pekai

16-Dec-03 3:50

Thank you, I will try to explain:

I used
[ProvideProperty("ImageIndex", typeof(MenuItem))]

to "add" the Property "ImageIndex" to MenuItem.

Now I want to move through all MenuItems by code and set the values of "ImageIndex".

(More abstract I would prefer to move through all components, check if they have the extended property "ImageIndex" and set the value)

Peter Kaiser

Heath Stewart16-Dec-03 4:05

16-Dec-03 4:05

You should really read about providers. You're doing it completely wrong. You can just add a property like that - you can extend the MenuItem and add properties and methods, or you can create a type designer or editor that can simulate a property at design-time and that writes out code to make use of that "virtual" property. Essentially, this is what IExtenderProviders are, and you must implement that interface and provide the Type as the second parameter to the ProvidePropertyAttribute. Be sure to read about those two things in the .NET SDK documentation.

This amounts to another component that actually stores the values on behalf of the attributes class (or rather, and instance of that class). So, the MenuItem doesn't actually have that property, but another components would. If you name the property ImageIndex, then your extender provider would have a SetImageIndex and GetImageIndex method, as well as some optional specially-named methods to help with serialization.

There is a great couple articles about extender providers, including an example of what you're trying to do (adding an image easily to a menu) here at CP:

Getting to know IExtenderProvider[^] by James T. Johnson
Menu Images using C# and IExtenderProvider - a better mousetrap![^] by Chris Beckett

It's always a good idea to try searching first before posting a question. Chances are that is has been asked / solved before and you'll get answers quicker than waiting for a reply.

Be sure to read the documentation for IExtenderProvider and ProvidePropertyAttribute as well.

pekai16-Dec-03 4:18

pekai

16-Dec-03 4:18

thank you...

I know, that MenuItem doesn't actually have that property!
I know whta you wrote me about the extender provider and his set and get-methods!
I also know about the metioned articles, because I used Menu Images!

I just wanted to know, if there is a chance to find out if there is a extender provider for a component, and how to get and set the values of its properties at runtime..

Peter Kaiser

Heath Stewart16-Dec-03 4:59