VB:

Dim dict = New Dictionary(Of String, String)()
For n As Integer = 0 To 10
    dict.Add("Key " + n.ToString(), "Value " + n.ToString())
Next
 
ComboBoxItem1.ComboBoxEx.DataSource = New BindingSource(dict, Nothing)
ComboBoxItem1.ComboBoxEx.DisplayMember = "Value"
ComboBoxItem1.ComboBoxEx.ValueMember = "Key"

C#:

Dictionary<string, string> dict = new Dictionary<string, string>();
for (int n = 0; n <= 10; n++) {
	dict.Add("Key " + n.ToString(), "Value " + n.ToString());
}
 
ComboBoxItem1.ComboBoxEx.DataSource = new BindingSource(dict, null);
ComboBoxItem1.ComboBoxEx.DisplayMember = "Value";
ComboBoxItem1.ComboBoxEx.ValueMember = "Key";