C# Adding Filter to combobox dropdown list

Question

Need some help with adding filter to my ComboBox drop down list(windows Forms Visual studio 2015)

The drop down is populated as per below:

Answer 1

In case you are using a Dictionary as data source, the following can be useful. I created a static function in the form to be able to reuse it as I have several ComboBox instances for which I wanted to have the same behavior. Simply call the function from the TextUpdate event passing the control name and the source dictionary.

private static void FilterComboBox(ComboBox combo, Dictionary dataSource)
{
  var filter = combo.Text;
  if (string.IsNullOrWhiteSpace(filter))
    return;

  var filteredItems = dataSource.Where(kv => kv.Value.Contains(filter)).ToDictionary(k => k.Key, k => k.Value);

  combo.DisplayMember = "Value";
  combo.ValueMember = "Key";
  combo.DataSource = new BindingSource(filteredItems, null);

  // this will ensure that the drop down is as long as the list
  combo.IntegralHeight = false;
  combo.IntegralHeight = true;

  combo.DroppedDown = true;
  
  // remove automatically selected first item
  combo.SelectedIndex = -1;
  combo.Text = filter;

  // set the position of the cursor
  combo.SelectionStart = filter.Length;
  combo.SelectionLength = 0; 
}