I also modified that vb.Net version to create a quick example of not using picturebox controls for the cards, just drawing images of the cards on the form. I get the spirit of your post, but it's a major PITA to lay out control arrays via code. That's screenloads of cut and paste, and a lot of hard coding. WAY easier to just drag and drop the images with a mouse, at design time. Some drag-and-drop functionality is built into the Control class, which implements very basic functionality required by classes that display information to the user. The Control class handles user input through the keyboard and mouse.
Drag-and-drop results from a combined use of the mouse and keyboard. It is worth noting that in the .NET Framework, the Form class? This means that the set of drag-and-drop features is common to all forms and controls. In VB.NET, you can handle the same or even different events for multiple objects very easily in code. This renders design-time support for control arrays unnecessary, so it doesn't exist.
If you want an array or collection of controls then you create it in code in exactly the same way you would an array of Strings or Integers or anything else. In Listing 4, you can see the source code of the WM_LBUTTONDOWN message handler. When the mouse button is depressed, notice whether the mouse is over the selected text.
If not, do as usual and yield to the base WndProc method. Otherwise, you can detect whether or not a drag operation has been started. A drag operation is defined as any movement of the mouse from the click point that exceeds a system measure. The .NET Framework uses the SystemInformation.DragSize constant to indicate this value.
Although undocumented in the .NET Framework, there's a better way to detect a drag operation called a Win32 API function. If you want to extend an existing control with drag-and-drop functionality, the first step is identifying the start event. For dragging text out of a TextBox, choose the MouseDown event. Setting up a drag operation is, in theory, pretty straightforward.
You write a handler for the start event, place a call to the DoDragDrop method that all Control and Form objects expose, and finalize the operation when the method returns and you know the outcome of the operation . Try writing a MouseDown event handler for a TextBox and you'll run into trouble right away. In the DragOver event, first, check the type of data being dragged.
If the drag-and-drop operation is not carrying plain text, the control refuses any drop. Otherwise, it determines the effect of the operation by looking at the state of the keyboard. The default effect, if allowed by the source, is Copy, meaning that the data is copied to the control and not removed at the source. If the CTRL key is held down, and the Move effect is allowed, the effect is set to Move. Later, the card images in pictureboxes, and then later, just drawing a bitmap at the location. The TextBox control, in fact, does a lot of work in the MouseDown window event.
To implement drag capabilities, you need to override the default behavior regarding text selection. To accomplish this, you can't just write handlers for known events; you really need to derive a new class and override the WndProc method. Overriding WndProc gives you enough power to control the message flow that makes each Windows Forms control reside and interact within the core Windows UI infrastructure. To write a successful WndProc override, you need to know a lot about Win32 SDK programming and messages. Drag-and-drop doesn't fulfill requirements, but it contributes to making your application appear more professional and easy to use.
In Windows Forms applications, drag-and-drop operations consist mostly of handling a series of events. By accomplishing a few mandatory steps and working with the information available in the event arguments, you can easily facilitate dragging and dropping files, text, and any other sort of serializable data objects. This article demonstrates how to import files from the Windows shell and how to enhance some UI controls to make them accept input via drag-and-drop. Notable examples are the TextBox and the PictureBox controls.
The fact that it's done in code doesn't mean that you have to write the code yourself though. That will automatically generate an event handler with all 20 Click events in the Handles clause. Classes that use unmanaged resources, need to clean up and release those resources back to the OS.
You should get into the habit of, especially before setting something to nothing, seeing if there is a .Dispose method (start typing .Dis..., and see if intellisense shows a Dispose method). If there is a Dispose method, then you should call that first so the class can release the unmanaged resources, and then set it to nothing, so the Garbage collector can clean up any managed resources when it deems it necessary. Set the SelectionStart property to an integer value that represents the 0-based index of the character in the control's buffer. At the same time, set the length of the selection to 0. As a result, the caret is moved close to the specified character.
How can you determine the index of the character at a certain mouse position? This message takes in the coordinates of a point within the TextBox's client area and returns the 0-based index of the nearest character. To send this message to the TextBox, you need to interop with the underlying Win32 infrastructure. The code in Listing 3 shows the interop .NET class that calls into a Win32 DLL.
The mouse down alone is not a reliable indicator that a drag-and-drop operation has started. When the mouse down event is fired, first store the coordinates at which the mouse button was pressed. More exactly, create a rectangle of a fixed and system-defined size centered around the point of click.
Next, when the MouseMove event arrives, verify that the current coordinates of the mouse point are outside that rectangle. If so, the user is moving the mouse enough to denote a real drag-and-drop action. The beginning of the drag-and-drop operation is marked with a call to DoDragDrop. You call this method from within the MouseMove event handler. To make the form or control the target of a drag-and-drop operation, you start by setting AllowDrop to True.
Next, handle the DragDrop event, indicating that the operation is complete. The event arguments include the data being moved and its format. In the handler of this event, the target of the drop decides what to do and how to refresh its own user interface in light of the drop. In VB6, I'd have a control array with 20 images laid out at design time, and all using the same imgFoo_click event handler.
And at the bottom of the loop you can see where four event handlers are added for each card, but all 52 cards point to the same four event handlers, as a VB6 control array would. I recently ported a vb6 program I wrote years ago to VB.Net 2010 in response to another thread in this forum. It is a card game which used a control array of pictureboxes for the cards. Is not having control arrays a showstopper rendering these old apps unable to be recreated in VS/VB 2013? Can someone point me to how this is done in the latest 2013 version?
Let's just say a simple example of having 3 labels on the screen, and setting their .text property via a run-time loop. However, for run-time loop processing of a group of controls , I think I do need to have them in an array or collection of some kind. When this is the case, then I do need to dynamically create the controls and add them into an array, correct? Or, can I still create the controls in design time, and then add them to a collection for run-time manipulation? This way, I can avoid the whole run-time creation of controls, yet still be able to manipulate them as a group/index at run-time...
In this article we will learn about some of the frequently asked C# programming questions in technical like "c# picturebox array how to create handler mouseover for element" Code Answer's. This article will show you simple practices on dealing with performance problems, starting with when you need to deal with them at all. You will see techniques to detect if a problem exists, find the specific cause, and fix it. Below are some solution about "c# picturebox array how to create handler mouseover for element" Code Answer's. Implementing drag-and-drop from within a TextBox control is more complicated than with other controls.
This is because the TextBox control handles the MouseDown event on its own; subsequently, custom code must interact with that implementation. Supporting a drag operation from a PictureBox control is significantly easier. If there is a change in the keyboard state (e.g., the CTRL key is pressed), the QueryContinueDrag event is also raised to ask the user whether to continue or conclude the operation.
The control's code determines what to do by setting a value in the event argument's data. If the operation must continue, the DragOver event is raised followed by the GiveFeedback event. The DragOver and GiveFeedback events arrive in a pair so that the user is given the most up-to-date feedback on the mouse's location. The AllowDrop property is useful if you want the form or control to accept data from external applications or controls. A form or control that only exports data through drag-and-drop doesn't need to set the value to True. I created a new project with one form, added a PictureBox with an image set at the image field from the properties of that PictureBox.
Then added that sc up there just to change the image from file. All the pictureboxes that you've click on an even number of times, have a new bitmap created from the Resource file, and since you don't dispose of them, you are creating more memory/resource leaks every time you toggle the image off. C# answers related to c# how to make label transparent c# picturebox array how to create handler mouseover for element wpf scrollviewer mouse wheel. Drag-and-drop is not reputed to be a feature that makes your application richer from a functional point of view.
What drag-and-drop does is make applications easier and more intuitive to use. In this article, I've discussed the basics of drag-and-drop in the .NET Framework, and focused on the members, the classes, and the model that makes it work. Next, I've provided a few practical examples including how to enhance TextBox and PictureBox controls to accept drops and drag their data out. DoDragDrop is the method that governs the whole drag operation. The method fires the proper events to the target and to the source as needed. When the method returns, the operation has completed and you must update the source accordingly.
You need to do nothing special if the drag ended in a copy. If it ends in a move, cut the selected text from the source TextBox. GiveFeedback is used to provide users with some feedback about the possible outcome of the ongoing operation, be it a copy, move, or link of the dragged data. Any call to GiveFeedback occurs within the initial call to the DoDragDrop method that any source control does to start a drag-and-drop operation.
DoDragDrop determines the control under the current cursor location and raises the event if the control is a valid drop target. To start a drag-and-drop operation, begin writing a handler for the control's MouseDown event. The event occurs whenever the mouse button is pressed within the control's bounds. Pressing the mouse button is the first low-level event in any drag-and-drop operation. Accomplishing drag-and-drop operations is done handling a series of events and setting a few properties, most notably the aforementioned AllowDrop property. Table 1 lists the key members involved in all drag-and-drop operations.
Drag-and-drop is one of those programming features rarely listed in the user requirements document because it is perceived as secondary and minor. Sure, drag-and-drop doesn't make your application run faster, nor does it add anything to the core business of the application. Drag-and-drop is not the solution to any core business issues and doesn't add any new functionality to the application. Yet drag-and-drop is a feature that, if missing, users promptly miss and are quick to add to the wish list for the next upgrade. If you would like the VB6 version for comparison it can be found post #5 of this thread on another site. There are various things you can do to simulate VB6 design-time support for control arrays to some degree but it's really pointless, other than to make things feel more familiar to someone coming from VB6.
It doesn't really achieve anything from the project's or application's perspective. Earlier in this article, I discussed how to drop a file name onto a PictureBox control and have it display the contained image, if any. And can you drag-and-drop images between PictureBox controls? To top off the code, consider that when you drop onto another control, you should make sure that the original selection is restored on the source.
At the same time, this should be avoided if the drag-and-drop takes place within the context of the same control. Figure 4 shows a sample application with two TextBox controls that support drag-and-drop. It's pretty common that a drag operation starts when a MouseDown event is fired.
Note that this is only the most intuitive scenario, certainly not a rule. Any event could be used to initiate a drag-and-drop procedure. Also note that certain controls have custom drag-specific events, as is the case with the ListView and TreeView controls. These controls fire the ItemDrag event to notify you that a drag operation is in course.
The DragDrop event handler retrieves the file name and attempts to extract the image in it. Note that at this point, no check has been made on the type of file. It can certainly be a JPEG as well as a TXT or a DOC file. You can filter the file type in the DragOver event or accept any file and try to render its contents as an image. The .NET Framework groups the most commonly used data formats in the DataFormats enum type. The GetData method extracts and returns the data of the specified format and GetDataPresent indicates whether data is available in a given format.
Finally, you use SetData to add data in a given format to the container being moved across controls. Let's review the sequence of events and related steps that occur when data is being dragged from, or dropped onto, a form or control. So, it looks like the "Handles" construct is one way to have a common event handler for a group of controls. This approach doesn't require dynamically creating the controls at run time.
