Indeed the RadTreeListView supports adding ColumnGroups
just as the RadGridView does.
Can you take a look at the Column Groups
article, where this feature is outlined? Note, that the article is for the RadGridView, however the same approach can be used with the RadTreeListView as well.
Can you check whether you have defined the GridViewColumnGroups in the ColumnGroups
collection of the RadTreeListView? Additionally, the Name
of the GridViewColumnGroup has to be the same as the ColumnGroupName
property of the column.
I hope you find this helpful.
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