CODEWITHSUNDEEP
wpfbindingtreeviewmvvm-lightsorteddictionary
Fred
Fred

Reputation: 607

wpf binding a TreeView to a SortedDictionary<string, List<Class>>

OK, once again, my Google-Fu isn't up to par and I would really appreciate a little guidance here.

I have a WPF app with multiple pages, one of which contains a TabControl, of which one of the tabs contains a grid, in which one of the columns contains a StackPanel with just two items on it: a Label and a TreeView. I have no need to update the TreeView once the content is obtained. The app uses MVVMLight (great toolkit!) to expose the data and said data is exposed in an mvvm (observable) property as it should be. I have checked and the data itself is available in correct form once I get to the point of setting the ItemsSource property so I know it's not the lack of data or the structure of the data itself. I have looked at all the entries on the web (at least the first 4 pages worth) matching the search terms "wpf treeview dictionary" and all articles come close, but don't get me to where I need to be. I'm missing something and what's worse, IntelliSense is even "helping" by providing the correct values for the xaml settings. So I know I'm close, but after two days of frustration, I'm throwing in the towel and asking for an assist.

So...to the meat of the problem: The data that the TreeView needs to display is in the form of SortedDictionary<string, List<ServerEntityNameMsSqlSvr>>. A ServerEntityNameMsSqlSvr class contains multiple properties, one of which is FullName. What I want the TreeView to display is the dictionary Key as the parent node and the FullName from each of the items in the List<ServerEntityNameMsSqlSvr>. You'd think that'd be simple, no? Not for me, the closest I can get is to display the Key of the dictionary, but either nothing for the children (best case) or throw an exception that stops the app with a null exception (worst case).

Here is the xaml I'm using (worst case):

<TreeView Grid.Column="0" ItemsSource="{Binding TableHierarchy}">
    <TreeView.ItemTemplate>
            <HierarchicalDataTemplate ItemsSource="{Binding Path=Value}">
                <TextBlock Text="{Binding Path=Key}"/>
                <HierarchicalDataTemplate.ItemTemplate>
                    <DataTemplate DataType="awe:ServerEntityNameMsSqlSvr">
                        <TextBlock Text="{Binding FullName}"/>
                    </DataTemplate>
                </HierarchicalDataTemplate.ItemTemplate>
            </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>

"TableHierarchy" is the MVVM property that exposes the data, it is declared as SortedDictionary<string, List<ServerEntityNameMsSqlSvr>>. The DataType "awe:ServerEntityNameMsSqlSvr" is a simple class with a few methods and properties, nothing special. One layer of inheritance, no interfaces. Of the properties that are available, I want to expose just the FullName, which is declared as public string FullName => _FullName(); Yep, it calls an overloaded method to build the full name but the result is a simple string (and the method call happens when the data is built, not a display time, iow, the values are already there, at least debugging to the setter shows that the content is correct.

Some of the solutions that I have researched suggest that the data type be changed to something other than a dictionary. In this case, that's not possible and given that the lists are, on occasion, quite large, I don't want to rebuild it into something else. This needs to work with the sorted dictionary as declared.

Upvotes: 0

Views: 204

Answers (1)

Fred
Fred

Reputation: 607

The xaml shown above is indeed correct, however, the gadget that supports the data (the methods in the ServerEntityNameMsSqlServer class) all need to not throw exceptions under any circumstances. In this case, one of the methods not directly involved with the author's code but used somewhere else in the framework (an overloaded call to "Equals" that was constructed to check individual property equality to determine the result) was throwing a null exception because a property wasn't filled in for the particular use case.

Difficult to find, but that was the cause.

Upvotes: 1

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