To reproduce:

-add RadMultiColumnComboBox and use the following code snippet: public partial class Form1 : Form { public Form1() { InitializeComponent(); List<Activity> list1 = new List<Activity>(); for (int i = 0; i < 5; i++) { if (i == 0) { list1.Add(new Activity() { Id = i, Name = "duplicated activity" }); } else { list1.Add(new Activity() { Id = i, Name = "Duplicated Activity" }); } } this.radMultiColumnComboBox1.DataSource = list1; this.radMultiColumnComboBox1.ValueMember = "Id"; this.radMultiColumnComboBox1.DisplayMember = "Name"; MultiColumnComboPopupForm popup = this.radMultiColumnComboBox1.MultiColumnComboBoxElement.MultiColumnPopupForm; popup.EditorControl.MasterTemplate.CaseSensitive = true; this.radMultiColumnComboBox1.SelectedValue = 2; } public class Activity { public string Name { get; set; } public int Id { get; set; }     } }

Workaround: initialize the selected value in the Load event.