Populate Windows Form CheckedListBox based on ComboBox selection using C# and VB.Net

Hi smile,

Refer elow sample.

Namespaces

C#

using System.Data.SqlClient;

VB.Net

Imports System.Data.SqlClient

Code

C#

private void Form1_Load_1(object sender, EventArgs e)
{
    using (SqlConnection con = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT EmployeeId, Country FROM Employees", con))
        {
            using (SqlDataAdapter da = new SqlDataAdapter(cmd))
            {
                DataTable dt = new DataTable();
                da.Fill(dt);
                DataRow row = dt.NewRow();
                row[0] = 0;
                row[1] = "Please select";
                dt.Rows.InsertAt(row, 0);
                this.comboBox1.DataSource = dt;
                this.comboBox1.DisplayMember = "Country";
                this.comboBox1.ValueMember = "EmployeeId";
            }
        }
    }
}

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    if (comboBox1.SelectedValue.GetType() != typeof(DataRowView))
    {
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT EmployeeId, Country FROM Employees WHERE Country =@Country", con))
            {
                cmd.Parameters.AddWithValue("@Country", comboBox1.Text);
                using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                {
                    DataTable dt = new DataTable();
                    da.Fill(dt);
                    this.clbCustomers.DataSource = dt;
                    this.clbCustomers.DisplayMember = "EmployeeId";
                    this.clbCustomers.ValueMember = "EmployeeId";
                }
            }
        }
    }
}

VB.Net

Private Sub Form1_Load_1(ByVal sender As Object, ByVal e As EventArgs)
    Using con As SqlConnection = New SqlConnection(constr)
        Using cmd As SqlCommand = New SqlCommand("SELECT EmployeeId, Country FROM Employees", con)
            Using da As SqlDataAdapter = New SqlDataAdapter(cmd)
                Dim dt As DataTable = New DataTable()
                da.Fill(dt)
                Dim row As DataRow = dt.NewRow()
                row(0) = 0
                row(1) = "Please select"
                dt.Rows.InsertAt(row, 0)
                Me.comboBox1.DataSource = dt
                Me.comboBox1.DisplayMember = "Country"
                Me.comboBox1.ValueMember = "EmployeeId"
            End Using
        End Using
    End Using
End Sub

Private Sub comboBox1_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
    If comboBox1.SelectedValue.[GetType]() <> GetType(DataRowView) Then
        Using con As SqlConnection = New SqlConnection(constr)
            Using cmd As SqlCommand = New SqlCommand("SELECT EmployeeId, Country FROM Employees WHERE Country =@Country", con)
                cmd.Parameters.AddWithValue("@Country", comboBox1.Text)
                Using da As SqlDataAdapter = New SqlDataAdapter(cmd)
                    Dim dt As DataTable = New DataTable()
                    da.Fill(dt)
                    Me.clbCustomers.DataSource = dt
                    Me.clbCustomers.DisplayMember = "EmployeeId"
                    Me.clbCustomers.ValueMember = "EmployeeId"
                End Using
            End Using
        End Using
    End If
End Sub

Screenshot