title: ComboBox item doesn't update even if case is changed
body: <p>I have a basic form with a combobox, a textbox, and a button on it. The combobox has an unalterable number of items within it, but the items themselves can be changed by inputting a new value for the selected item.</p>
  
  <p><img src="https://i.stack.imgur.com/VgE68.png" alt="enter image description here"></p>
  
  <p>From the example in the picture, if I input a string such as "identifier", the selected item in the combobox changes from "ID" to "identifier", as expected. However, if I input "id", the logic (below) executes normally, the item updates, but visually, the item does not change from "ID" to "id".</p>
  
  <p>Here is the code for the event handler of the button</p>
  
  <pre><code>private void btnApply_Click(object sender, EventArgs e) {
  
      string newValue = txtNewName.Text;
  
      if(string.IsNullOrWhiteSpace(newValue)) {
          MessageBox.Show("Please input a new column name");
          return;
      }
  
      if(cmbHeaderNames.Items.Contains(newValue)) {
          MessageBox.Show("A column with that name already exists");
          return;
      }
  
      cmbHeaderNames.Items[cmbHeaderNames.SelectedIndex] = newValue;
  
      txtNewName.Text = "";
  
  }
  </code></pre>