title: Winforms ComboBox User Control Binding
body: <p>I have a user control that inherited from Combobox control. I want to bind data in the constructor of the user control. but when I add it to form and run the project it shows duplicated items.</p>
  
  <p>When I add control to my winform its add items in the Designer file of form and when I run project it added again in constructor of user control. </p>
  
  <pre><code>public partial class CheckSeriesBox : ComboBox
  {
      private static List&lt;string&gt; CheckSeries;
  
      public CheckSeriesBox()
      {
          InitializeComponent();
  
          CheckSeries = new List&lt;string&gt;();
          SetCheckSeries();
  
          this.Items.AddRange(CheckSeries.ToArray());
          this.SelectedIndex = 0;
      }
  
      public static List&lt;string&gt; SetCheckSeries()
      {
          CheckSeries.Add("A");
          CheckSeries.Add("B");
      }
  }
  </code></pre>