HOW TO: Populate a TreeView Control from a Dataset in Visual Basic .NET (320755)

SUMMARY

This step-by-step article describes how to display data from a hierarchical dataset by using the TreeView control in Microsoft Visual Basic .NET. To do this, you establish a parent, child, and grandchild relationship, and then fill the TreeView control appropriately. The TreeView control has a Nodes collection with root TreeNode objects. Each TreeNode object has its own Nodes collection that holds more than one child TreeNode object. You can then use the TreeView control to work down from the parent or root node to the corresponding child nodes and display the appropriate data.

This example creates a hierarchical dataset, loops through each table, and adds nodes to the TreeView control for each child table in the dataset.

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Requirements

The following list outlines the recommended hardware, software, network infrastructure, and service packs that are required:

• Microsoft Visual Studio .NET installed on a compatible Microsoft Windows operating system
• A SQL server with the sample Northwind database installed

This article assumes that you are familiar with the following topics:

• Visual Basic .NET
• ADO.NET data access

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Create the Project and Add Code

1. Start Visual Studio .NET, and then create a new Visual Basic Windows Application project.
2. Add a reference to System.Data.SQLClient by adding the following line to the top of your Form1.vb file:

   Imports System.Data.SqlClient
   					

3. Drag a TreeView control (Treeview1) from the toolbox to your form (Form1).
4. Open the form's code window, and then paste the following code into the Form1_Load event:
   Note You must replace USER ID <user name> and PASSWORD <strong password> with the correct values. Make sure that the USER ID has the appropriate permissions to perform these operations on the database.
   

           Dim DSNWind As DataSet
           Dim CNnwind As New SqlClient.SqlConnection("DATA SOURCE=servername;USER ID=<username>;PASSWORD=<strong password>;INITIAL CATALOG=northwind;") '<==== CHANGE HERE 
           Dim DACustomers As New SqlClient.SqlDataAdapter("SELECT CustomerID, CompanyName, ContactName, Country FROM customers WHERE country = 'Germany'", CNnwind)
           Dim DAOrders As New SqlClient.SqlDataAdapter("SELECT CustomerID, OrderID, OrderDate, ShippedDate, ShipVia, Freight FROM orders where customerid in (select customerid from customers where country = 'Germany')", CNnwind)
           Dim DAOrderDetails As New SqlClient.SqlDataAdapter("Select * from [Order Details] where OrderID in (SELECT OrderID FROM orders where customerid in (select customerid from customers where country = 'Germany'))", CNnwind)
   
           DSNWind = New DataSet()
           CNnwind.Open()
           DACustomers.Fill(DSNWind, "dtCustomers")
           DAOrders.Fill(DSNWind, "dtOrders")
           DAOrderDetails.Fill(DSNWind, "dtOrderDetails")
           'Close the connection to the data store; free up the resources
           CNnwind.Close()
   
           'Create a data relation object to facilitate the relationship between the Customers and Orders data tables.
           DSNWind.Relations.Add("CustToOrd", DSNWind.Tables("dtCustomers").Columns("CustomerID"), DSNWind.Tables("dtOrders").Columns("CustomerID"))
           DSNWind.Relations.Add("OrdToDet", DSNWind.Tables("dtOrders").Columns("OrderID"), DSNWind.Tables("dtOrderdetails").Columns("OrderID"))
           '''''''''''''''''''''''
           TreeView1.Nodes.Clear()
           Dim i, n As Integer
           Dim parentrow As DataRow
           Dim ParentTable As DataTable
           ParentTable = DSNWind.Tables("dtCustomers")
    
           For Each parentrow In ParentTable.Rows
               Dim parentnode As TreeNode
               parentnode = New TreeNode(parentrow.Item(0))
               TreeView1.Nodes.Add(parentnode)
               ''''populate child'''''
               '''''''''''''''''''''''
               Dim childrow As DataRow
               Dim childnode As TreeNode
               childnode = New TreeNode()
               For Each childrow In parentrow.GetChildRows("CustToOrd")
                   childnode = parentnode.Nodes.Add(childrow(0) & " " & childrow(1) & " " & childrow(2))
                   childnode.Tag = childrow("OrderID")
                   ''''populate child2''''
                   ''''''''''''''''''''''''''
                   Dim childrow2 As DataRow
                   Dim childnode2 As TreeNode
                   childnode2 = New TreeNode()
                   For Each childrow2 In childrow.GetChildRows("OrdToDet")
                       childnode2 = childnode.Nodes.Add(childrow2(0))
   
                   Next childrow2
                   ''''''''''''''''''''''''
   
               Next childrow
               '''''''''''''''
           Next parentrow
   					

5. Modify the connection string point to point to the Northwind database on your SQL server.
6. Press CTRL+F5 to run the program.

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