Archive for category Controls

WPF: Access Keys Scoping

Problem

Within the WPF framework access keys are always scoped to the active window, regardless of what settings you may have set. This can cause problems when multiple elements exist within the window hierarchy. The WPF framework will likely choose the incorrect target element. What you need is to scope the access keys to the currently focused element, and unfortunately the WPF framework contains a internal bug that prevents this functionality.

Solution

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WPF: IsSynchronizedWithCurrentItem and ICollectionView Cancel Bug

Problem

As some of you may have noticed while working with a Selector-derived control and an ICollectionView, there is a bug with the IsSynchronizedWithCurrentItem property of Selector.  IsSynchronizedWithCurrentItem is provided by Selector to support the ability to keep its SelectedItem in-sync with the CurrentItem of its ItemSource’s ICollectionView. IsSynchronizedWithCurrentItem works perfectly except for one specific case: when the CurrentChanging event of ICollectionView is handled and the item change is cancelled.

In this case the Selector does not respect the cancel and it gets out-of-sync with the ICollectionView. I’d imagine this bug exists because the Selector class was likely implemented before ICollectionView, and Selector was not updated to match the addition. Whatever happened though the bug does exist in WPF 4.0 and can be very problematic. Luckily, with attached properties at our disposable we can work up an easy fix.

Solution

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WPF: DataContext for ContextMenu

Problem

Often times WPF  developers want to throw their computer out the window because of a small and very irritating truth about the ContextMenu control. I’m talking about the fact that ContextMenu is not in the same visual tree as its containing parent, resulting in many data binding issues. Since the ContextMenu is not in the same visual tree, ElementName, RelativeSouce (FindAncestor), etc bindings will not work. You can get around this through the use of the PlacementTarget property and some complex DataContext re-routing, but it is a pain, confusing, and does not scale well (at all). I will present a very simple attached property that relieves the situation.

Solution

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WPF: DataGrid ContextMenu for Column Visibility

Introduction

When dealing with software applications it is commonplace for users to have certain expectations. These expectations not only include the abilities of an application, but also include how such abilities are executed. The specific expectations that this article is focused upon directly concern those of the data grid control, and more specifically Microsoft’s implementation of such a control under the Windows Presentation Foundation (WPF) user-interface rendering sub-system for Windows-based applications.

Users have come to expect the ability to hide or show the columns of a data grid control. Such an action is typically executed by right-clicking on any of the data grid’s column headers. This results in the option to select a menu item, via a context menu, that will toggle the visibility of the column labeled on the menu item. Therefore providing this ability with access to execute its associated actions in the typical way, would be a wise and logical decision. The implementation of meeting this need should be provided through an encapsulated and reusable interface. Unfortunately, Microsoft’s implementation of the data grid control does not offer this functionally as a built-in feature and adding it has proving to be a difficult task.

In this article you will be provided with a solution that implements this functionality specifically for Microsoft’s implementation of the data grid control. This solution has proving reliable regardless of whether the data grid’s columns have been auto-generated through the data in which it represents, while still conforming to the generally accepted Model-View-ViewModel (MVVM) design pattern guidelines. This has been accomplished by utilizing WPF’s attached properties system whose means provide the ability of separate child elements to specify unique values on properties defined in a parent element; thus providing the ability to manipulate the parent element’s behavior indirectly. In this way the concepts of encapsulation and reuse have been applied.

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WPF: DataGrid Select-all-button Styling

Problem

The SelectAll button on Microsoft’s DataGrid control cannot be styled without a workaround. This is a direct result of there being no SelectAllButtonTemplate property on the control. To get around this issue we’ll make our own property using attached properties. This way we can have nice, clean, MVVM-compliant code and XAML-markup, while still getting what we want.

Solution

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WPF: Non-selectable ListBoxItem and ListViewItem

Problem

Sometimes in WPF you want to have a list of items contained in a ListBox (or ListView) that you don’t want to be selectable. You could set those items to be disabled, by assigning IsEnabled to False, but that may interfere with styles among other things. You could also (probably the best idea) use a ItemsControl, from which the ListBox derives, that doesn’t include selectable-items functionality. However, for whatever reason, you may just want to use a ListBox (or ListView) instead.

Solution

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