CheckComboBox WPF Extended Toolkit
<p>I have a <strong>database table</strong> named <strong>Charges</strong> in SQL Server having <strong>three columns</strong>(ChargeName, Charge, Type). 
Here is the snapshot of the populated table below:</p>

<p><a href="https://i.stack.imgur.com/kxVaC.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/kxVaC.png" alt="Snapshot"></a></p>

<p>I am using Extended WPF Toolkit's <strong>CheckComboBox</strong> Control. I wanted to print the selected items from dropdown.</p>

<p>Here is my XAML code file</p>

<pre><code>&lt;Window x:Class="RTS_Management.TestScreen"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:xctk="clr-namespace:Xceed.Wpf.Toolkit;assembly=Xceed.Wpf.Toolkit"
    Title="TestScreen" Height="300" Width="300"&gt;
&lt;Grid&gt;
    &lt;StackPanel Orientation="Vertical"&gt;
        &lt;StackPanel Orientation="Horizontal"&gt;
            &lt;TextBlock Margin="5"&gt;Purpose: &lt;/TextBlock&gt;
            &lt;xctk:CheckComboBox x:Name="_combo" 
                         HorizontalAlignment="Center" 
                         VerticalAlignment="Center" 
                         DisplayMemberPath="ChargeName"
                         ValueMemberPath="ChargeName"

                          /&gt;
            &lt;Button Name="display" 
                    Click="display_Click"
                    Margin="5"&gt;
                Display Selected
            &lt;/Button&gt;
        &lt;/StackPanel&gt;

    &lt;/StackPanel&gt;
&lt;/Grid&gt;
</code></pre>

<p></p>

<p>And this is the <strong>Code Behind File</strong></p>

<pre><code>using MessageBox = System.Windows.MessageBox;

namespace RTS_Management
{
    /// &lt;summary&gt;
    /// Interaction logic for TestScreen.xaml
    /// &lt;/summary&gt;
    public partial class TestScreen : Window
    {
        bool handle = true;
        public TestScreen()
        {
            InitializeComponent();
            BindTreatmentComboBox(_combo);
        }

        // displaying data in ComboBox
        public void BindTreatmentComboBox(CheckComboBox comboBoxName)
        {
            string ConString = ConfigurationManager.ConnectionStrings["RTS_ManagementModel"].ConnectionString;
            string CmdString = string.Empty;
            SqlConnection conn = new SqlConnection(ConString);
            try
            {
                conn.Open();
                CmdString = "SELECT ChargeName "
                    + "FROM Charges ";
                SqlDataAdapter da = new SqlDataAdapter(CmdString, conn);
                DataSet ds = new DataSet();
                da.Fill(ds, "Charges");
                comboBoxName.ItemsSource = ds.Tables["Charges"].DefaultView;
                //comboBoxName.ItemsSource = ds;

            }
            catch (Exception ex)
            {

                Xceed.Wpf.Toolkit.MessageBox msg = new Xceed.Wpf.Toolkit.MessageBox();
                msg.ShowMessageBox(ex.Message.ToString());
            }
            finally
            {
                conn.Close();
            }
        }

        private void display_Click(object sender, RoutedEventArgs e)
        {
            MessageBox.Show(_combo.SelectedValue.ToString());
        }
    }
}
</code></pre>

<p>What I am missing? Guys help me I am not good at WPF.</p>