TreeDataGrid's Expand/Collapse button

[nasterhe]

This triangle is too difficult to select, is there any way to change it to a cross and a button that starts with a word like a Windows tree? Thanks.

[msneijders]

Looks like this is its default template. (<ControlTheme x:Key="TreeDataGridExpandCollapseChevron" TargetType="ToggleButton" \>) Change it to something you want it to look like.

[nasterhe]

Thanks.I can define a ControlTheme following the code you prompted, but I don't know how to use the ControlTheme to override ToggleButton theme in the TreeDataGridExpanderCell.

<Style Selector="TreeDataGridExpanderCell /template/ ToggleButton">
  <Setter Property="Theme"  Value="{StaticResource MyTreeDataGridExpandCollapseChevron}"/>
 </Style>

This code didn‘t work.

[msneijders]

I don't know why you cannot override Theme like this. But I think you will soon find the need to change TreeDataGridExpanderCell template as well to get what you want.

If you copypaste Generic.axaml, and remove everything except the ControlThemes for TreeDataGridExpandCollapseChevron and TreeDataGridExpanderCell, put it in your own MyTreeDataGrid.axaml and StyleInclude it in your App.axaml, then it will work.

And when you need to change other treedatagrid primitives, you can simply copypaste it again and tweak what you want.

[msneijders]

I don't know why you cannot override Theme like this.

I think this has to do with BindingPriority and Setter precedence. Where a simple Style selector gets priority "Style", and the Theme assignment inside the template has "Template", which has higher precedence.

But you can "lift up" the BindingPriority to "StyleTrigger" if you add a class name; and then it gets precedence over Template:

<Style Selector="TreeDataGrid.test TreeDataGridExpanderCell /template/ ToggleButton">
    <Setter Property="Theme" Value="{StaticResource MyTreeDataGridExpandCollapseChevron}" />
</Style>

<TreeDataGrid Classes="test" />

Just learned something new ;). But if you want your styling in all of your treedatagrid instances, the previous way is easier imo.

[nasterhe]

Thanks.It's worked.