I have an app with 2 DataGridView's and have implemented Drag/Drop to allow the user to move data between them. Within the context of my application dragging rows between two instances of a form isn't a meaningful action. I'm not sure how to detect it in drag enter so that I can set e.Effect to DragDropEffects.None.
If I don't do so and set it to Copy the DragDrop event fails with a cryptic exception "This remoting proxy has no channel sink which means either the server has no registered server channels that are listening, or this application has no suitable client channel to talk to the server."
While I can trap this exception to prevent a crash from happening, and abort the actual drop of data in the process it's bad practice to do so, and could be confusing to the user since the drop allowed cursor would be shown but no drop would take place.
Microsoft says that any control can accept data from a drag-and-drop operation in progress, and that you can designate a control as a drop zone by setting the AllowDrop property to true. I would think that, if you set AllowDrop to false on those controls that you do not wish to be a drop zone, you should get the desired behavior.
If you want to detect drag and drop between two instances of your program, you can set an ID in the dragging object (i.e. put a GUID in the tag of the control), and check it during the drag process to see if it matches the GUID of your currently running instance.
http://msdn.microsoft.com/en-us/library/ms973845.aspx
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I have a problem with a Windows Store app.
I have a view; on this view I display data that can be modified in this view.
Once the user finishes modifying the information, they have to click on a "Finish" button to store in a database the information.
But when there is too much information to store the treatment takes a long time and the UI is open to user actions. If the user makes an action, my application throws an exception because data were not present any more for the control.
So I searched for a way to block the UI (like a messagedialog: Wait while your data is being stored). I tried with a message dialog, but once I tap on yes my storage method is launched and the message dialog is directly closed, so the user can create an exception with his action.
My question is: how to block the UI while doing a treatment in Windows Store apps?
You can do the trick by adding the Grid on whole page content with, for example, ProgressBar. Then show it when you perform long operations and you want to avoid user interactions with the app. When operation finished, just change state of your page (hide Grid from the top).
The other way to do it, if you don't have a lot of elements of UI to block, is to set IsHitTestVisible property of your Buttons and other clickable elements to false when you perform operations.
I am making a custom OPC Client application in WPF to communicate with a Kepware server. One of the functions is to configure a tag, including setting it's host and server. Now I could do this manually with calls to the Kepware ClientAce API for searching for valid network hosts and valid servers on that host, but ClientAce includes a .dll that already provides a tree control the user can browse directly. However, this out of the box control is in Windows Forms.
So I have this WPF Window that I launch as Modal Dialog with ShowDialog(). Within this window is a WindowsFormsHost element that contains the aforementioned server browsing control. It's works pretty well for the most part, including providing an event to handle when the user has made a new selection in the tree control. That event has a boolean parameter that indicates if the new selection is a server. A good thing since that's the very thing I'm trying to keep track of here.
It also provides a "server has been double-clicked" event, which I handle and have decided to interpret as a shortcut to the user selecting that server as the one they want. (Otherwise, they have to click a separate button for the currently selected server which I stored based on the aforementioned selection event.)
All good so far....
...But! There is another functionality Kepware added (well actually there's a few, but I'm not worried about those at this point). The user has the ability from a context menu to delete a server from the tree. For some reason, this is throwing a null exception (though, it successfully deletes the server from the tree). This is a very bad thing for my purposes because...:
I don't have any idea what leads to this. There is no stack trace. There is no extra information. Just that something, somewhere in that control has thrown an unhandled exception that I must now deal with.
I can't remove the context menu item. There's another context menu item that I can set a property in the XAML to remove, but that one isn't throwing the exception. It's the one I can't remove that is.
There's a lovely event called "ContextMenuItemClicked". It'd be nice if I could handle that. I just go into my handler, put a try/catch around the logic, and ignore the null exception that has absolutely nothing to do with me and what I'm trying to accomplish. However, the universe is against me here, and has decided that this is a mouse-click event, which Windows Forms doesn't want to propogate. I've searched around and this seems to be a common issue with Windows Forms and WPF interop. Mouse-clicks just don't play nice with the interop services. I tried. I really did. But the handler I made just sits there unused. Odd thing is, while I can understand why I can handle the "SelectionChanged" event from this control, I'm curious as to what Kepware did to make the "ServerDoubleClick" event propogate up, and why they didn't decide to extend that same courtesy to the context menu click.
So there I am. With an exception that isn't my fault, that I don't care about, and I apparently can't prevent. I just want to throw it away and move on. However, it's in a modal dialog, and I need to have this exception handled before the method that called ShowDialog() and popped this window up in the first place. (I'll spare you the details as to why. This post is long-winded enough as it is.)
Is there a way I can either somehow propogate the mouse events up, or trap this exception somewhere in my window class so that it doesn't propagate up the stack into the calling method?
I have an application that contains multiple MemoEdit controls containing DevExpress spell checkers. When a user updates the Options (through a MemoEdit's context menu), we are saving those options to our db. Is there any built-in way to broadcast those new options to all spell checkers in the application? It's probably worth noting that some of the MemoEdits are used in Interop controls in the VB6 "part" of our application.
Right now I'm using events, but things aren't working out as well as I'd hoped and before I get too deeply into rolling my own fix I figured I'd ask the SO folks.
Thanks in advance for any tips.
My tech lead and I just acquired dev express subscription for a win forms application we are building and we are using the spellchecker and saving the options to our sql server ce table. We have multiple forms with one spellchecker each tied to one memo edit control per form.
I programmed a single reusable function named “GetSpellCheckerOptions” which returns type “DevExpress.ExtraSpellChecker.OptionsSpelling” that loads the six options from the spell check options dialog form from our sql server ce table. This function is invoked in a form’s constructor where the form has the spellchecker component associated to it and this can be any form in our application. It is built around an “on-demand” basis as opposed to loading it in memory and keeping it around for the lifetime of the application because the notes or comments being written by our users are on forms that load, fill it out and close.
You can use the event called OptionsChanged which is a member of the type “DevExpress.ExtraSpellChecker.OptionsSpelling”. You will have hook up the event in runtime using a subroutine you write like this for example:
jobsSpellChecker.OptionsSpelling.OptionChanged += new EventHandler(this.jobsSpellChecker_OptionChanged);
When a user changes an option on the spell check options dialog this event will fire, however there are some gotchas to be aware of. When the event fires you will not know which option fired the event because the Event Argument does not provide that information. So I save as a whole save regardless of which options were changed. The save occurs after the OK button is clicked as opposed per option being changed. The biggest gotcha is that this event fires three times. Two of those three times is from something totally unrelated to changing an option. So to control the two unneed event fires you need an if statement evaluating the options form dialog result, like this for example,
if(jobsSpellChecker.FormsManager.OptionsForm.DialogResult == System.Windows.Forms.DialogResult.OK)
This will protect your save code from being executed needlessly. In addition without the “if” statement the control has a nasty way of remembering previous state of what the options were before you changed them and during those unneeded two of three event fires, it changes your options setting from the new desired settings back to previous state or settings. Very annoying and it has taken the whole day to get past these obstacles and more experimenting with these controls. Hopefully this information can offer you or someone else a value that will save time, avoid potential frustration and endless browsing product support pages.
Msdn doc for IsolatedStorageFile.IncreaseQuotaTo states that:
To increase the quota, you must call
this method from a user-initiated
event, such as in an event handler for
a button-click event. When you call
the IncreaseQuotaTo method, the common
language runtime in Silverlight
presents a dialog box for the user to
approve the request. If the user
declines the request, this method
returns false and the quota remains
the same size.
How does Silverlight know that the method was called from a user-initiated event like a button click and not from some other thread?
More specifically: What is a user initiated event? Is there any way to overcome this limitation?
And another question:
I do some automatic downloads of files when user first accesses my application, but I don't want the user to press "Download" and then when I detect more space is needed call IncreaseQuota and have the "Silverlight dialog" appearing asking for more space.
I want to start the download automatically (not user initiated), and if I detect more space is needed, call IncreaseQuota and hence have the "Silverlight dialog" appear. (No user pressing download).
After much digging, I did find out what a user initiated event is. Seems that msdn doc specifies what a user initiated event in the section related to "events overview", but there's no link between documentation of IsolatedStorageFile.IncreaseQuotaTo and Events Overview
So a user initiated event according to the definition is:
Silverlight enforces that certain
operations are only permitted in the
context of a handler that handles a
user-initiated event. The following is
a list of such operations:
Setting IsFullScreen.
Showing certain dialogs. This includes
SaveFileDialog, OpenFileDialog, and
the print dialog displayed by
PrintDocument.Print.
Navigating from a HyperlinkButton.
Accessing the primary Clipboard API.
Silverlight user-initiated events
include the mouse events (such as
MouseLeftButtonDown), and the keyboard
events (such as KeyDown). Events of
controls that are based on such events
(such as Click) are also considered
user-initiated.
API calls that require user initiation
should be called as soon as possible
in an event handler. This is because
the Silverlight user initiation
concept also requires that the calls
occur within a certain time window
after the event occurrence. In
Silverlight 4, this time window is
approximately one second.
User-initiated event restrictions also
apply to usages of JavaScript API for
Silverlight.
When Silverlight is in full-screen
mode, some input events are
deliberately limited for security
reasons, although this can be
mitigated for out-of-browser
applications using elevated trust. For
more information, see Full-Screen
Support.
Although I don't see "IncreaseQuotaTo" inside the list of "operations", I'm guessing they just forgot it, since the behavior/limitations are the same as the ones described in the doc.
I was curios how exactly does silverlight know what a user initiated event is but after digging through .net framework source code I've got to a dead end:
if ((browserService == null) || !browserService.InPrivateMode())
{
//..
}
return false; //means that IncreaseQuota will fail
where browser.IsInPrivateMode is:
[SecuritySafeCritical]
public bool InPrivateMode()
{
bool privateMode = false;
return (NativeMethods.SUCCEEDED(UnsafeNativeMethods.DOM_InPrivateMode(this._browserServiceHandle, out privateMode)) && privateMode);
}
where DOM_InPrivateMode is in a DllImport["agcore"] which according to microsoft is confidential :(
So it looks like I won't find out soon how they're detecting user initiated events.
Thinking it more about it, I guess microsoft didn't want a user to have many tabs open in a browser and then poof: I call automatically IncreaseQuotaTo.
The IncreaseQuotaTo is a browser modal dialog. This means you can't navigate to other browser tabs while is active.
So if the user has now moved from my page to the tab with google.com, and if I would be able to call IncreaseQuotaTo with a delay, the user might think that google.com is asking for more storage :).
This would be a security breach indeed.
Had they implemented this with a page level dialog, then that would have been probably more easily hacked (or worked around).
So all in all, thinking of it, I'm starting to see why they implemented it like this and why these limitations exist.
The documentation isn't incomplete.
If I do this... button_click(..) { new UserControl() }... Does this still count as a user initiated event?
Yes. But what has that little bit of extra code really achieved?
What i've personally never experimented with is exactly what consitutes a user event; IOW is a mouse-over considered a user event? This will be very simple for you to try, and there are a multitude of other things you can experiment with. If necessary you could have a splash screen popup that welcomes the user and they have to click on it to dismiss it, at which point you make the request. It may seem a bit corny, but you can get away with things like this if you present it well.
Note that the prompt is a one-time thing. If you prompt the user and they accept, that storage is persisted for your application between visits, which means you don't need to prompt them again the next time they use your control, your quota is still increased from last time (unless the user has deliberately deleted it, which they can do by right clicking on the Silverlight control and then going to the Application Storage tab).
I have an application that runs elevated (yes, it has to be elevated) but it needs to detect when another application is dragging an object over it. My application doesn't care what the object is, it doesn't want to receive the object, it just needs to know if something is being dragged. In a normal application this isn't an issue, but because my application is elevated it doesn't receive any of the standard drag/drop events from lower privilege applications. Is there a programmatic way to detect whether the cursor is involved in a drag/drop operation?
To do "system wide" drag and drop, I think you have to go the OLE way.
Drag and Drop (OLE)
Also see the "Data Objects and Data Sources (OLE)" link at the bottom of the article.