title: NULL Empty Item in Bound ComboBox
body: <p>How can I have an empty item in the bound <code>ComboBox</code> which uses <code>NULL</code> as the value for an Insert or Update?</p>
  
  <p>With the code below, I can manually add the additional row.  The column <code>inspector_id</code> is the primary key of an FK relationship.  I have to set <code>inspector_id = -1</code>, since C# does not allow an <code>int</code> to be <code>null</code>.  However, the insert (or update) fails since there is no <code>inspector_id: -1</code> in the database.</p>
  
  <pre><code>private void ItemInfo_Load(object sender, EventArgs e)
  {
      // TODO: This line of code loads data into the 'someDBDataSet.inspector' table. You can move, or remove it, as needed.
      this.inspectorTableAdapter.ClearBeforeFill = false;
      someDBDataSet.inspectorRow newRow = this.someDBDataSet.inspector.NewinspectorRow();
      newRow.inspector_id = -1; // Since an int in C# cannot be null
      newRow.fullName = "(none)";
      newRow.employeeCode = "";
      this.someDBDataSet.inspector.AddinspectorRow(newRow);
  
      this.inspectorTableAdapter.Fill(this.someDBDataSet.inspector);
      //this.inspectorTableAdapter.ClearBeforeFill = false;
      // TODO: This line of code loads data into the 'someDBDataSet.item' table. You can move, or remove it, as needed.
      this.itemTableAdapter.Fill(this.someDBDataSet.item);
  }
  </code></pre>