How to show/hide empty groups in RadListView control.

Environment

Product Version	Product	Author
2023.2.718	RadListView for WinForms	Dinko Krastev

Description

In this particular case, we will demonstrate how we can hide an empty group without deleting it or adding a new one.

Solution

Subscribe to the VisualItemFormatting event. In the event handler, we can get the ListViewDataItemGroup and hide it if it does not contain any items. This way when you run the application, you can observe that the "Empty Group" is not visible. The group will appear when an item is added to it.

public Form1()
{
    InitializeComponent();
    this.radListView1.VisualItemFormatting += RadListView1_VisualItemFormatting;
    for (int i = 0; i < 10; i++)
    {
        this.radListView1.Items.Add("Item" + i);
    }
    radListView1.EnableCustomGrouping = true;
    radListView1.ShowGroups = true;
    ListViewDataItemGroup docGroup = new ListViewDataItemGroup("Documents");
    ListViewDataItemGroup diskGroup = new ListViewDataItemGroup("Disks");
    radListView1.Groups.Add(docGroup);
    radListView1.Groups.Add(new ListViewDataItemGroup("Empty Group") { });
    radListView1.Groups.Add(diskGroup);
    foreach (ListViewDataItem item in radListView1.Items)
    {
        if (this.radListView1.Items.IndexOf(item) % 2 == 0)
        {
            item.Group = docGroup;
        }
        else
        {
            item.Group = diskGroup;
        }
    }

    this.radListView1.AllowArbitraryItemHeight = true;
}

private void RadListView1_VisualItemFormatting(object sender, ListViewVisualItemEventArgs e)
{
    SimpleListViewGroupVisualItem groupItem = e.VisualItem as SimpleListViewGroupVisualItem;
    if (groupItem != null)
    {
        ListViewDataItemGroup group = groupItem.Data as ListViewDataItemGroup;
        if (group.Items.Count == 0)
        {
            //hide the group arrow
            groupItem.ShowHorizontalLine = false;
            groupItem.ToggleElement.Visibility = ElementVisibility.Collapsed;
            groupItem.DrawText = false;
        }
        else
        {
            groupItem.ShowHorizontalLine = true;
            groupItem.ToggleElement.Visibility = ElementVisibility.Visible;
            groupItem.DrawText = true;
        }
    }
    else
    {
        e.VisualItem.DrawText = true;
    }
}

Public Sub New()
    InitializeComponent()
    AddHandler Me.radListView1.VisualItemFormatting, AddressOf RadListView1_VisualItemFormatting

    For i As Integer = 0 To 10 - 1
        Me.radListView1.Items.Add("Item" & i)
    Next

    radListView1.EnableCustomGrouping = True
    radListView1.ShowGroups = True
    Dim docGroup As ListViewDataItemGroup = New ListViewDataItemGroup("Documents")
    Dim diskGroup As ListViewDataItemGroup = New ListViewDataItemGroup("Disks")
    radListView1.Groups.Add(docGroup)
    radListView1.Groups.Add(New ListViewDataItemGroup("Empty Group"))
    radListView1.Groups.Add(diskGroup)

    For Each item As ListViewDataItem In radListView1.Items
        Dim index As Integer = Me.radListView1.Items.IndexOf(item)

        If index Mod 2 = 0 Then
            item.Group = docGroup
        Else
            item.Group = diskGroup
        End If
    Next

    Me.radListView1.AllowArbitraryItemHeight = True
End Sub

Private Sub RadListView1_VisualItemFormatting(ByVal sender As Object, ByVal e As ListViewVisualItemEventArgs)
    Dim groupItem As SimpleListViewGroupVisualItem = TryCast(e.VisualItem, SimpleListViewGroupVisualItem)

    If groupItem IsNot Nothing Then
        Dim group As ListViewDataItemGroup = TryCast(groupItem.Data, ListViewDataItemGroup)

        If group.Items.Count = 0 Then
            groupItem.ShowHorizontalLine = False
            groupItem.ToggleElement.Visibility = ElementVisibility.Collapsed
            groupItem.DrawText = False
        Else
            groupItem.ShowHorizontalLine = True
            groupItem.ToggleElement.Visibility = ElementVisibility.Visible
            groupItem.DrawText = True
        End If
    Else
        e.VisualItem.DrawText = True
    End If
End Sub