Custom Sorting
Custom sorting is a flexible mechanism which allows you to replace the default sorting logic with your own logic. The custom sorting operation has higher priority that the default sorting.
To apply your own logic for sorting, you have to create a class which inherits from TreeNodeComparer and override its Compare method, where you can add your custom logic. Here is a sample where we will reverse the sorting of the tree i.e. when sorting Ascending we will actually sort in Descending order and vice versa.
Creating custom comparer
class MyComparer : TreeNodeComparer
{
public MyComparer(RadTreeViewElement treeView)
: base(treeView)
{
}
public override int Compare(RadTreeNode x, RadTreeNode y)
{
if (this.TreeViewElement.SortOrder == SortOrder.Descending)
{
return x.Text.CompareTo(y.Text);
}
return x.Text.CompareTo(y.Text) * -1;
}
}
Class MyComparer
Inherits TreeNodeComparer
Public Sub New(treeView As RadTreeViewElement)
MyBase.New(treeView)
End Sub
Public Overrides Function Compare(x As RadTreeNode, y As RadTreeNode) As Integer
If Me.TreeViewElement.SortOrder = SortOrder.Descending Then
Return x.Text.CompareTo(y.Text)
End If
Return x.Text.CompareTo(y.Text) * -1
End Function
End Class
Once the comparer is created we have to assign it to the RadTreeView control:
Assign the custom comparer
radTreeView1.TreeViewElement.Comparer = new MyComparer(this.radTreeView1.TreeViewElement);
RadTreeView1.TreeViewElement.Comparer = New MyComparer(Me.RadTreeView1.TreeViewElement)
To test this scenario, you can add a button and a label to the form, where you will change and print the sort order. This will allow you to check whether the sorting is reversed:
private void radButton1_Click(object sender, EventArgs e)
{
if (radTreeView1.SortOrder == SortOrder.None)
{
radTreeView1.SortOrder = SortOrder.Ascending;
radLabel1.Text = "Sorting: Ascending";
}
else if (radTreeView1.SortOrder == SortOrder.Ascending)
{
radTreeView1.SortOrder = SortOrder.Descending;
radLabel1.Text = "Sorting: Descending";
}
else
{
radTreeView1.SortOrder = SortOrder.None;
radLabel1.Text = "Sorting: None";
}
}
Private Sub RadButton1_Click(sender As System.Object, e As System.EventArgs)
If RadTreeView1.SortOrder = SortOrder.None Then
RadTreeView1.SortOrder = SortOrder.Ascending
radLabel1.Text = "Sorting: Ascending"
ElseIf RadTreeView1.SortOrder = SortOrder.Ascending Then
RadTreeView1.SortOrder = SortOrder.Descending
radLabel1.Text = "Sorting: Descending"
Else
RadTreeView1.SortOrder = SortOrder.None
RadLabel1.Text = "None"
End If
End Sub
