Hello,

I tested the case from the example here: https://docs.telerik.com/devtools/maui/controls/listview/grouping/property-group-descriptor and the groups are collapsed as expected. 

The behavior to return null could be the code is executed before the data is populated in the control. 

For example, I added a button and execute the code on a button click, then the groups collapsed

    private void Button_Clicked(object sender, EventArgs e)
    {
        var data = this.listView.GetDataView();
        data.CollapseAll();
    }

Regards,
Didi
Progress Telerik

Declined due to insufficient information.

Regards,
Didi
Progress Telerik

Hello David,

Thank you for reaching out.

I have tested the RadListView GetDataView method in our SDK Demo App and I cannot reproduce any issues.

We would require more information about the scenario in which the method is used to be able to help with the solution.

I look forward to your reply.

Regards,
Antoan
Progress Telerik