Tag Archives: .Net

How is a WPF XAML file tied into the application’s executable environment?

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By hidden source code file…

A hidden source code file is auto-generated for each WPF XAML file. The names used for this file and for the class it contains are based off the XAML file’s filename. In a C# application, the file MyWindow.xaml will have a hidden code-behind file named MyWindow.g.cs containing a class named MyWindow.

…containing a class…

The contained class inherits from the WPF core class corresponding to the associated XAML file’s root element. If the root element in the XAML file is <Window>, the class in the hidden code-behind file will inherit from Window.

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Keeping the Selected Item Selected When Changing a ListView’s ItemsSource

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A ListView’s data display needs to be updated. The revised dataset, retrieved from the service layer, is contained in a new collection containing new object instances. Setting this IList<T> as the control’s new ItemsSource causes the control to display the revised data and…whoa…clears the currently selected item.

From the technical perspective, this clearing makes sense. A new collection has been displayed making the selected item from the previous collection irrelevant. However, from the user’s perspective, the same collection is displayed both before and after the refresh (albeit with revised data), so the current item selection is still pertinent and should be maintained.

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Event Arguments == Static Snapshots?

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Is the event argument that’s passed to an event handler/handler override always a non-changing snapshot taken the moment the event occurred?

No! While convention suggests a “yes” answer, no technical constrain enforces this assumption (as I discovered recently). The properties of an event argument can (and sometimes do) return information about the current (live) state of the system instead of describing the moment the event occurred.

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DataGrid – Per-Row Running Totals

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The program I’m working on lists transactions in a WPF Toolkit DataGrid. Each grid row displays a transaction’s date, amount, etc.  Each row in the grid needed to show the sum of all transaction amounts prior to and including that row. You might call this a per-row running total. Example:

Date       | Check #   | Payee       | Amount    | Balance
2/1/10                   Frank         10.00       10.00
3/6/10       101         John          -6.95        3.05
4/9/10       102         Tom           -1.05        2.00

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