Sorting

As expected from a sophisticated databound control, RadTreeList offers sorting capabilities that allows the users to conveniently order the items in the desired direction. To enable this functionality you just have to set AllowSorting property to true and the control will handle the sorting operations automatically.

There are three sort modes:

• Ascending - orders the items in ascending order.

• Descending - orders the items in descending order.

• None - the items are ordered in the way they came from the data source ("Natural" sort).

RadTreeList also supports sorting by multiple data fields - this is the so-called Multi-column sorting. To enable this mode, set the AllowMultiColumnSorting to true.

Sorting in RadTreeList

Due to the self-referencing nature of the control, the sorting takes effect "per-level". Basically,this means that each level of the hierarchical structure is sorted independently. The screenshot below illustrates this behavior:

Sorting API

RadTreeList exposes the following properties and methods:

Example 1: Declarative Approach of setting the SortExpressions

<telerik:RadTreeList ID="RadTreeList1" runat="server" DataSourceID="SqlDataSource1" AllowSorting="True" ...>
    <SortExpressions>
        <telerik:TreeListSortExpression FieldName="EmployeeName" SortOrder="Ascending" />
    </SortExpressions>
</telerik:RadTreeList>

Example 2: Programmatic Approach of setting the SortExpressions

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        TreeListSortExpression sortExpr = new TreeListSortExpression();
        sortExpr.FieldName = "EmployeeName";
        sortExpr.SortOrder = TreeListSortOrder.Ascending;
        RadTreeList1.SortExpressions.AddSortExpression(sortExpr);

        RadTreeList1.Rebind();
    }
}

Protected Sub Page_Load(sender As Object, e As EventArgs)
    If Not IsPostBack Then
        Dim sortExpr As New TreeListSortExpression()
        sortExpr.FieldName = "EmployeeName"
        sortExpr.SortOrder = TreeListSortOrder.Ascending
        RadTreeList1.SortExpressions.AddSortExpression(sortExpr)

        RadTreeList1.Rebind()
    End If
End Sub