Special character displays as square in TreeView in C# and VB.Net

Hi aginell4life,

Using this article i have created the example and didn't find any issue with special characters.

Populate TreeView from Database in Windows Forms using C# and VB.Net

Database

I have used following Vehicle Access Database to populate the TreeView.

VehicleTypes

VehicleSubTypes

Namespaces

C#

using System.Data;
using System.Data.OleDb;

VB.Net

Imports System.Data
Imports System.Data.OleDb

Code

C#

private void Form1_Load(object sender, EventArgs e)
{
    DataTable dt = this.GetData("SELECT Id, Name FROM VehicleTypes");
    this.PopulateTreeView(dt, 0, null);
}

private void PopulateTreeView(DataTable dtParent, int parentId, TreeNode treeNode)
{
    foreach (DataRow row in dtParent.Rows)
    {
        TreeNode child = new TreeNode
        {
            Text = row["Name"].ToString(),
            Tag = row["Id"]
        };
        if (parentId == 0)
        {
            treeView1.Nodes.Add(child);
            DataTable dtChild = this.GetData("SELECT Id, Name FROM VehicleSubTypes WHERE VehicleTypeId = " + child.Tag);
            PopulateTreeView(dtChild, Convert.ToInt32(child.Tag), child);
        }
        else
        {
            treeNode.Nodes.Add(child);
        }
    }
}

private DataTable GetData(string query)
{
    string constr = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Dharmendra\Desktop\Vehicle.accdb";
    using (OleDbConnection con = new OleDbConnection(constr))
    {
        using (OleDbDataAdapter sda = new OleDbDataAdapter(query, con))
        {
            using (DataTable dt = new DataTable())
            {
                sda.Fill(dt);
                return dt;
            }
        }
    }
}

VB.Net

Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
    Dim dt As DataTable = Me.GetData("SELECT Id, Name FROM VehicleTypes")
    Me.PopulateTreeView(dt, 0, Nothing)
End Sub

Private Sub PopulateTreeView(dtParent As DataTable, parentId As Integer, treeNode As TreeNode)
    For Each row As DataRow In dtParent.Rows
        Dim child As New TreeNode() With {
                .Text = row("Name").ToString(),
                .Tag = row("Id")
            }
        If parentId = 0 Then
            treeView1.Nodes.Add(child)
            Dim dtChild As DataTable = Me.GetData("SELECT Id, Name FROM VehicleSubTypes WHERE VehicleTypeId = " & child.Tag)
            PopulateTreeView(dtChild, Convert.ToInt32(child.Tag), child)
        Else
            treeNode.Nodes.Add(child)
        End If
    Next
End Sub

Private Function GetData(query As String) As DataTable
    Dim constr As String = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\Dharmendra\Desktop\Vehicle.accdb"
    Using con As New OleDbConnection(constr)
        Using sda As New OleDbDataAdapter(query, con)
            Using dt As New DataTable()
                sda.Fill(dt)
                Return dt
            End Using
        End Using
    End Using
End Function

Screenshot