To reproduce:
- Add the following column to a blank grid and new row or edit the existing one:
GridViewMaskBoxColumn maskBoxColumn = new GridViewMaskBoxColumn();
maskBoxColumn.Name = "Dates";
maskBoxColumn.HeaderText = "Dates";
maskBoxColumn.MaskType = MaskType.FreeFormDateTime;
maskBoxColumn.DataType = typeof(System.DateTime);
radGridView1.MasterTemplate.Columns.Add(maskBoxColumn);
this.radGridView1.Rows.Add(DateTime.Now.AddDays(5));