Settings GridViewColumn.DisplayIndex Breaks GridViewColumnGroup.Header Showing

[Jimmy]

Hello

In a release of WPF after 2015.2.728 (up to and including 2020.2.617) the ability to programatically set the DisplayIndex of a GridViewColumn was broken, in what seems to be a bug (it used to work fine, and I'm not sure what behaviour you could achieve with this bug in place).  I haven't pinpointed the release, as a lot of releases have happened during that time!

I've attached a simple example which demonstrates this bug, you just have to change the boolean constant in the code behind file from `false` to `true`, and you'll see that the group header no longer shows.  If you go back to release 2015.2.728 then this works, but now it only works if you set DisplayIndex to -1 (anything else causes an argument exception, as there's a mismatch to the number of columns, which makes sense).  If you don't have the header group then you can obviously change the DisplayIndex as required, but as soon as you do, it breaks the header grouping.

I'd post the code solution if I could, but it's pretty simple, you don't even need the public class in my code behind, that's there just to make the column group header obvious.

 

Thanks!

[Jimmy]

Also, much of the XAML isn't required either, again it's just to make it obvious where the column group header is.  You can trim it down to just the RadGridView if you like.

[Vladimir Stoyanov]

Hello Jimmy,

Thank you for the shared pictures. 

I was able to replicate the same result on my end and I have logged a new item in our feedback portal: GridView: ColumnGroup is not displayed when the Columns DisplayIndex is set when they are initialized. I have also added some telerik points to your account as a thank you for bringing this to our attention.

As a workaround, for the moment, you can set the DisplayIndex of the columns after they are created. Here is what I have in mind:

public partial class MainWindow : Window
    {
        private const string ColumnGroupName = "MyColumnGroup";
        public MainWindow()
        {
            InitializeComponent();

            var displayIndex = -1;
            this.RadGridView1.Columns.AddRange(
                new[]
                {
                    new Telerik.Windows.Controls.GridViewColumn
                    {
                        ColumnGroupName= ColumnGroupName,
                        Header = "Column A",
                    },
                    new Telerik.Windows.Controls.GridViewColumn
                    {
                        ColumnGroupName= ColumnGroupName,
                        Header = "Column B",
                    },
                    new Telerik.Windows.Controls.GridViewColumn
                    {
                        ColumnGroupName= ColumnGroupName,
                        Header = "Column C",
                    }
                }

            );

            foreach (var col in this.RadGridView1.Columns)
            {
                col.DisplayIndex = ++displayIndex;
            }

            var columnGroup = new GridViewColumnGroup
            {
                Name = ColumnGroupName,
                Header = "Test"
            };
            this.RadGridView1.ColumnGroups.Add(columnGroup);
            
        }
    }

I hope you find this helpful.

Regards,
Vladimir Stoyanov
Progress Telerik

[Jimmy]

Thanks Vladimir, that's very much appreciated