![]() ![]() To do this we have to hook up handlers on the PreviewMouseMove and PreviewMouseLeftButtonDown events. To start the drag operation, we have to detect a mouse move while the left mouse button is pressed. Get the data by calling the GetData() method on the Data object provided in the event args. When the user releases the mouse button the DragDrop event is called.If the data can be dropped, set the Effect property on the event args to display the appropriate mouse cursor. Check the format and the data by calling GetDataPresent() on the event args. Register a handler to the DragEnter event to detect a dragging over the drop location.Set the AllowDrop property to True on the elements you want to allow dropping.Initiate the dragging by calling DoDragDrop().Find the data you want to drag and create a DataObject that contains the format, the data and the allowed effects.Detect a drag as a combinatination of MouseMove and MouseLeftButtonDown.This article shows how simple drag and drop can be implemented in WPF. ![]() But only a few programmers provide drag and drop functionality in their applications, because they think its much more dificult than it really is. Once again the solution is data binding, which we'll look into in the next chapters.Drag&Drop can drasticly improve the productiviy and user experience of a software. Situations, and while you could do it from Code-behind instead, this would have resulted in even more lines of code. While it is entirely possible to define an entire TreeView just using markup, as we did in the above examples, it's not the best approach in most Because we're defining the entire thing with simple markup, you can do almost anything, but as you can see from the example code, it doesĬome with a price: Huge amounts of XAML code, for a tree with just six nodes in total! Summary I did a whole bunch of things here, just to show you the kind of flexibility you get: I colored the child items and I added images and even buttons to the You're rewarded with a lot more flexibility than you could ever get from the WinForms TreeView. With the WPF TreeView, it's a bit more complex, but This is very easy to do with WinForms, because the TreeView is built exactly for this scenario. One of the common requests from people coming from WinForms or even other UI libraries is the ability to show an image next to the text label of a TreeView Shows us that we can stuff pretty much whatever we want to into the Header property instead of just a string and then have the TreeView render it - a greatĮxample of why it's so easy to customize the look of WPF controls. As you can see, I can just specify a text string and then have it rendered directly withoutĭoing anything else, but this is WPF being nice to us - internally, it wraps the text inside of a TextBlock control, instead of forcing you to do it. ![]() The Header is an interesting property, though. ![]() TreeViewItem's with images and other controls By default, a TreeViewItem is not expanded, but to show you the structure of the example, I have used the IsExpanded property to expand the two parent items. To specify the text we want displayed for each node, we use the Header property. The TreeView control and its child objects are also child tags to its parent object. We simply declare the TreeViewItem objects directly in the XAML, in the same structure that we want to display them in, where the first tag is a child of This is indeed very easy to get started with, as you can see from the example here: The TreeView control: A simple TreeView exampleĪs we talked about in the previous article, the WPF TreeView can be used in a very simple manner, by adding TreeViewItem objects to it, either fromĬode-behind or simply by declaring them directly in your XAML. ![]()
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