How to: Bind the ASPxTreeList to Data Created at Runtime

• Dec 17, 2020
• 2 minutes to read

This example shows how to bind the ASPxTreeList to data created at runtime.

Note

To correctly restore from the ViewState, a tree list needs data. When binding to data created at runtime, you must bind the tree list within the Page_Init event. Don’t handle the Page_Load event because it is fired after the ViewState has been restored.

C#

using System.Data.OleDb;
using DevExpress.Web.ASPxTreeList;

public partial class _Default : System.Web.UI.Page {
    protected override void OnInit(EventArgs e) {
        base.OnInit(e);
        InitTreeList(ASPxTreeList1);
    }

    protected void Page_Load(object sender, EventArgs e) {
        ASPxTreeList1.DataBind();
        (ASPxTreeList1 as IPostBackDataHandlerEx).ForceLoadPostData(Tree.ID, HttpContext.Current.Request.Params);
    }

    OleDbDataAdapter CreateDataAdapter() {
        string connectionString =
        @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Databases\Departments.mdb";
        OleDbConnection myConnection = new OleDbConnection(connectionString);
        string query =
        "SELECT [ID], [ParentID], [Department], [Budget], [Location] FROM [Departments]";
        return new OleDbDataAdapter(query, myConnection);
    }
    DataTable CreateDataTable(OleDbDataAdapter myAdapter) {
        DataTable dt = new DataTable();
        DataSet testData = new DataSet();
        myAdapter.Fill(testData);
        return testData.Tables[0];
    }
    void InitTreeList(ASPxTreeList tl) {
        tl.SettingsSelection.Recursive = true;
        tl.SettingsSelection.AllowSelectAll = true;
        tl.SettingsSelection.Enabled = true;
        tl.KeyFieldName = "ID";
        tl.ParentFieldName = "ParentID";
        tl.DataSource = CreateDataTable(CreateDataAdapter());
    }
}

VB.NET

Imports Microsoft.VisualBasic
Imports System
Imports System.Data
Imports System.Configuration
Imports System.Web
Imports System.Web.Security
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Web.UI.WebControls.WebParts
Imports System.Web.UI.HtmlControls
Imports System.Data.OleDb
Imports DevExpress.Web.ASPxTreeList

Public Partial Class _Default
    Inherits System.Web.UI.Page
    Protected Overrides Sub OnInit(ByVal e As EventArgs)
        MyBase.OnInit(e)
        InitTreeList(ASPxTreeList1)
    End Sub

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
         ASPxTreeList1.DataBind()
        (ASPxTreeList1 as IPostBackDataHandlerEx).ForceLoadPostData(Tree.ID, HttpContext.Current.Request.Params)
    End Sub

    Private Function CreateDataAdapter() As OleDbDataAdapter
        Dim connectionString As String = _
        "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Databases\Departments.mdb"
        Dim myConnection As OleDbConnection = New OleDbConnection(connectionString)
        Dim query As String = _
        "SELECT [ID], [ParentID], [Department], [Budget], [Location] FROM [Departments]"
        Return New OleDbDataAdapter(query, myConnection)
    End Function
    Private Function CreateDataTable(ByVal myAdapter As OleDbDataAdapter) As DataTable
        Dim dt As DataTable = New DataTable()
        Dim testData As DataSet = New DataSet()
        myAdapter.Fill(testData)
        Return testData.Tables(0)
    End Function
    Private Sub InitTreeList(ByVal tl As ASPxTreeList)
        tl.SettingsSelection.Recursive = True
        tl.SettingsSelection.AllowSelectAll = True
        tl.SettingsSelection.Enabled = True
        tl.KeyFieldName = "ID"
        tl.ParentFieldName = "ParentID"
        tl.DataSource = CreateDataTable(CreateDataAdapter())
    End Sub
End Class