Improving 'code-behind' compatibility

[flucas1]

Currently I use the 'Semi' theme for the TreeDataGrid.

It is easy to apply the theme from code behind using something like this.:

                    TreeDataGridSemiTheme treeDataGridSemiTheme = [];
                    Styles.Add(treeDataGridSemiTheme);

The DialogHost package also allows something similar

            global::DialogHostAvalonia.DialogHostStyles dialogHostTheme = [];
            Styles.Add(dialogHostTheme);

Ideally I would like to be able to do

                    global::Avalonia.Controls.TreeDataGrid.Themes.Simple themeSimpleTreeDataGrid = new();
                    Styles.Add(themeGenericTreeDataGrid);

                    global::Avalonia.Controls.TreeDataGrid.Themes.Fluent treeDataGridFluentTheme = new();
                    Styles.Add(treeDataGridFluentTheme);

rather than referencing the xaml by string...

This creation directly referencing objects helps with AOT and Trimming scenarions when using code-behind.

[flucas1]

As per

https://github.com/irihitech/Semi.Avalonia/blob/main/src/Semi.Avalonia.TreeDataGrid/TreeDataGridSemiTheme.axaml.cs

The change should be to create a pair of dummy files like that one.

Mabye another one to create an empty Resources file including the Generic.xaml, and call it Simple to keep the themes naming consistent.